It will be grayed-out in that 'Open Wallet' list if it's loaded
and the wallet should be selectable in the "Wallet:" drop-down menu at the right-hand side of Bitcoin Core:

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If the PM is about sending the wallet.dat, please don't send it to anyone including me.

Problem is, OP didn't followed anything based from his last reply (which I replied to).
My reply has different goal, it is to cross-check the actual address that he typed in localbitcoins with his Electrum's receiving address.
Plus (in my reply's case) why would you have to go to a blockexplorer if you can already see the transaction's output in the app/website itself?

So you've withdrawn Bitcoins from localbitcoins?
It couldn't be the fee since 1sat/B is enough for now.

Check if it's sent to the correct address:
Go to your localbitcoin's wallet transaction history, look for the withdrawal transaction that you did and check its "receiving address".
Open your Electrum and see if that address is in your 'Addresses' tab, ("View->Show Addresses" to enable the tab).
If it's not there, you've sent it somewhere else.

I hope that you've closed Bitcoin Core when you're swapping the wallet.dat files or there will be issues during the scan process of those wallet files.
(you said you've watch video tutorials so they must have mentioned it)

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The "wallet-test.dat" is in the "test wallet" folder so it won't be included to the open wallet selection menu, it should be outside that folder, but inside the 'wallets' folder.
The folders inside the 'wallets' folder are considered as 1 wallet (the wallet name is the folder's name) and it will use the wallet.dat file inside it.
If you want to use a renamed wallet.dat file, you should paste it in 'wallets' folder's root, not in the other folders inside it.

Only 1 wallet shows in the "Wallets:" drop-down menu because you've replaced the test wallet's wallet.dat with the old wallet, so the one's recognized by Bitcoin Core is the old wallet.
If there's no balance, it's either the wallet is empty or it there's an issue with the scan process.
Since you've disabled pruned settings (and have enough disk space?), you can use -rescanblockchain command to try to rescan for the wallet's balance but the current wallet may have issue already if you've swapped them while Bitcoin Core is open.

If you properly swapped them, you can enter rescanblockchain into the 'console' (Window->Console) and wait for it to finish (note: it will take a while to finish and may look like it's syncing but it's not actually downloading anything)

If you improperly swapped them, you can just do this instead:

• Close Bitcoin Core.
• Get a copy of the old wallet and rename the copy into "old_wallet.dat"
• Go to 'wallets' folder and copy old_wallet.dat into it (not inside test wallet folder).
• Open Bitcoin Core and it should be in the menu "File->Open wallet", select "old_wallet" and it will be loaded.
• Once it finished scanning, the correct balance should show-up.

The "legit" version in the official repository in Github: https://github.com/jackjack-jj/pywallet
There's an official thread posted here on Bitcointalk: Pywallet 2.2: manage your wallet [Update required]

But "up-to-date"? Not much.

That's normal since you just replaced the wallet.dat inside it.
This is why I'd suggested to rename the copy of the old wallet.dat and paste it inside the 'wallets' folder so Bitcoin Core would recognize both wallets when using the 'load wallet' menu.
Bitcoin-qt will be able to recognize renamed wallet.dat and 'folders with wallet.dat' in that folder using 'Open Wallet' menu.

Replacing the wallet.dat was good for the old version when there's no multi-wallet support, but now Bitcoin Core can handle multiple wallets at the same time.

This is also normal because Bitcoin Core will not create the data directory after being installed.
For the wallets folder, it will be created once you've created the first wallet.

It seems like you're watching some quite old video tutorials when Bitcoin Core automatically creates a "default wallet" when started the first time.

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By the way, the dumpwallet command in my post above can be used even without downloading the blockchain.
You can immediately export the keys and addresses right after loading the wallet.dat.

You don't have to, if you really need to prune, you just have to make sure that the wallet is loaded before syncing Bitcoin Core so it won't have to use rescan.
In your case, you wont have to resync again after it's done since you've now loaded the wallet (see if it's selectable from the "Wallet:" drop-down menu at the right).

You can use pywallet that's suggested by NotATether.

Or natively, use dumpwallet command to export all of the keys plus their respective addresses but you have to start Bitcoin Core first with "legacy" as the default address type because the dumpwallet file's addresses will be based from it; because you've mentioned that the wallet is from 2011~2013.

If you want to do it:

• Open Bitcoin Core's settings: "Settings->Options...->"; Click "Open configuration file"
• Type in the text editor that will open: addresstype=legacy and save it, then restart Bitcoin Core.
• Open Bitcoin Core, go to Console: "Window->Console", select the correct wallet from the drop-down menu of the console.
• Type the command: walletpassphrase "your_password" 120 to unlock the wallet (do not if it's not encrypted | "120" is to unlock it for 2minutes)
• Within the specified time, type dumpwallet "walletdump.txt" to create a dump file, you can change the name of the file if you want
  or specify the absolute path if you want to save it to another directory. e.g.: dumpwallet "E:\folder\walletdump.txt" (useful if Bitcoin Core doesn't have write permission in the install directory).
• Find the file in Bitcoin Core's installation directory where Bitcoin-qt is located or the specified absolute path and open it with a text editor.

The addresses (and their private keys) should be listed there.
Be careful with the file's contents since it contains the private keys which can be used to spend your wallet's funds.

You can also rename a copy of the wallet.dat file then paste it in that folder,
And in Bitcoin Core, use the menu: "File->Open wallet", select that wallet from the list and it will be loaded and will rescan (that could take a while to complete).

But no one mentioned but it's important that "prune" setting must be disabled when you started the initial blockchain download or else, you'll have to resync Core after loading the wallet file.
The setting is in: "Settings->Options..->Prune block storage to", it will also resync to disable that setting.

What do you mean by "key phrases", your wallet's passphrase (password)?
If you don't have it, you'll just waste your time syncing core since it will ask you the passphrase once you want to send the funds out.
Your only option is to bruteforce but you need to have some password candidates or at least some parts of it.

If you mean the "seed phrase" or "mnemonic" or "backup phrase", Bitcoin Core never supported seed phrase backup.

For the record, this only happens when you clicked "save" instead of "broadcast" when increasing the fee through rbf.

Reason is simple: the low-fee transaction is already in your history and the replacement that you want to save locally has the same inputs and outputs so it can't be saved.

Those are smart devices that "tried" to connect to your Local Network (WiFi) such as SmartTV, SmartPhones, etc.
Event though they failed because of wrong password attempt, those will still temporarily show up in your Windows File Explorer's Network.

If those are persistent, then there's most likely rogue devices connected to your Local Area Network, and check your router's settings.
I'd recommend disabling WPS if you're not using it.

For the logs, there's no sensitive info included there (aside from your windows account name if it's your real name).
Users who need support share it most of the time without issues;
in fact, it's recommended to include it to your post for faster support: [Pinned topic] [READ BEFORE POSTING] Tech Support Help Request Format

I can only assume that there's a bottleneck in your hardware,
I haven't used an NUC device but it seems like comparable to same-generation RPi models when it comes with specs,
I've heard that it'll take weeks to fully sync Core with it, -reindex on the other hand is also resource intensive minus the internet bandwidth.

Sadly, I can't help much if it's the hardware since I don't use either devices.

Are there any other errors beside that line? It indicates a corrupted file.
Usually, you just have to -reindex to fix it but you already on the process so there must be an issue somewhere else.
Maybe it's still not done with the reindex because of the hardware since you're using a NUC device and an external SSD.

You can try to speed it up by using more of your RAM by increasing the "database cache" by a reasonable amount (Settings->Options...->Size of database cache).
Set a value depending on your usual RAM usage (e.g. Half), but do not set it too high.

While you're in the settings, see if you have "pruning" setting enabled since you might not be needing it because you have enough space in your external SSD.
Plus reindex will trigger a full resync if your blockchain is pruned.

The % above is just for the "block headers", the one below is for the entire blockchain (the actual sync progress).

Try to set the specific block hash as 'valid' again by using the command reconsiderblock followed by the marked-invalid block hash.
You can input the command in the console tab (Window->Console)

Example:

It must be it, answers 3 & 4 'speaks for itself'.
If the bitcoin-equivalent amount is computed by their platform, then they are indeed miscalculating the deposit amount (in BTC).

Or have you been using the dollar input box in Electrum's 'send' tab instead of 'BTC' when sending to the casino?
Because every platform is using different APIs to get the market price, the fiat price will not be the same for all platforms.
If so, the selected source in Electrum's 'fiat' setting must have a different market price than the one used by Tigergaming.

This shouldn't be an issue since Electrum will not deduct the fee from the output's amount, except if you've replaced it via rbf ("increase fee" option) and selected the option to do so.

In that case, check the transactions in your Electrum's history tab (Right-click->View Transaction).
And see if the output (your poker site deposit address) has the same amount as what they've credited you.

If not the same, then they are either lying about the amount being deposited or there's an issue with their site.
If it's the same, then there's "something" wrong with your Electrum or setting (but definitely not a hack since the funds would've been wiped if so).

If that happens, you don't have to restore the watch-only wallet, the saved "local transaction" can be removed by the right-click menu "remove".

That sometimes happen if the server you're connected to somehow dropped it from their mempool,
or since you're using a cold-storage set-up, you may have clicked "save" instead of broadcast after loading the signed transaction.
Either way, it will be saved as a 'local transaction', indicated by the 'blue computer' icon instead of the 'check', 'pie' or 'clock' icon.
Example:

There may be issues with the latest header(s) that you've received and for some reason, Bitcoin Core may have invalidated it.
Try to check your logs for error lines about "block headers".

Log file is in the 'data directory' named "debug.log".

Yes, only if you're referring to the "root key" in your paper backup.
Armory is a "Hierarchical Deterministic" wallet which means that every private keys and addresses that it will generate can be recreated by the root key.

Otherwise, a single exported private key can only restore an address; one private key can only restore its address pair, not the whole wallet.

IDK if there's a way to get a 'master private key' from the 'root key' to be able to create a "versatile backup" but the instructions in the reply above you should be sufficient in case you need to export to another client.

While the GitHub repository and site use the trustworthy "bitcoinjs-lib.js" and the hashes checks out,
it's still using an outdated version 3.3.2 which might contain bugs that were fixed within that 4-year gap.

Anyways, why don't you just create a paper wallet using Bitcoin Core, Electrum or other trusted clients?
You just have to export the private key of the address that you picked.
It's basically the same except for the fancy wallet layout that you can print.