Shouldn't it be Electrum since it acts as the lightning node, not the server?

If that's the case, this might be the one you're looking for: https://electrum.readthedocs.io/en/latest/merchant.html#lightning-payments.

Okay, so that's the issue in the "Lightning Network Walktrough" thread is all about.

Unfortunately, I haven't found a way to open channels between two Electrum wallets either.
I have tried adding the "IP Address" but it always results with "Timeout" or "Cancelled Error".

You can try it: instead of using just the nodeid, follow it with an '@' sign then the PC/ISP's IP address like for example:
0369c4ddc6076646ddf30ad58c4beca8eee399557063f69a17xxxxxxxxxxxxxxxxx@17x.1xx.2x.4x
Both Electrum wallets should be active.

Because, you'll have to pay a fee that might take a portion of it to spend that balance because you'll end up with lots of very small inputs.
Transaction fee will be based from the fee rate (which you'll set in the wallet) and the transaction's virtual size which will get higher if it has a lot of inputs.
1sat/B is still good enough to consolidate them though.

Custodial wallets will just send from their hot wallet when you want to withdraw (minus their fee which can be cheaper for low-priority).
Personally, I'll use a custodial wallet for that amount.

LN is a very good choice however won't let you receive 'savings' from your 'clients' unless you have enough inbound capacity.
And you don't have enough funds to open a channel of 0.002 BTC then use submarine swap or spend some satoshi.
You need to find a way to increase your inbound capacity like mentioned in the previous sentence.

I don't get it.
But everything you can do with mainnet, you can do the same with testnet.

No, LN is only available for [standard] Native SegWit Electrum wallets.
Read the thread I linked above to learn more about the usage of Electrum's LN feature: Electrum Lightning Network walkthrough

Testnet funds have no value and in a separate blockchain than Bitcoin's and the testnet wallets will be saved in a different directory.
You can easily get funds using testnet faucets: List of Testnet BTC Faucet

0.002 plus the fees to open a channel.
Then use "reverse swap" to get some of the funds you don't need back to onchain, but that process comes with a fee of 0.0002+ BTC.

Or launch Electrum with -testnet argument to use testnet's chain for testing purposes.

0.002BTC being "good enough" is my personal opinion like I said above.
Other wallets however, will let you open a channel with lower amount IIRC maybe Electrum devs would reduce this in the future.
I can't recommend others though since I'm not using them.

BTW, long-term saving with that amount though LN is a no go, I suggest custodian wallets for amounts like 0.00069376 a year.
Reason is, you can't receive at all if you don't have inbound capacity, read this thread for more info: Electrum Lightning Network walkthrough: Receiving a payment

That error was due to your attempted open channel's fund is lower than 0.000547BTC.
You'll get a different error if it's lower than Electrum's minimum which is Exception('funding_sat too low: xxxx < 200000')

Unfortunately, there's no settings to override it.

I prefer it that way, because if the channel's funds is too low, users will end up opening channels more often if they need to send more funds.
If it's 0.002, they will only need that channel to transact LN funds given that the remote node has enough connections.

Plus, you can get your Bitcoins back to onchain funds and get inbound capacity though "submarine swap" feature which is very convenient to use in the GIU.

It looks like the same error as this:
electrum.lnutil.ConnStringFormatError: Don't know any addresses for node: ******
I got that when I tried to open a channel between two Electrum wallets.

That's probably because Electrum's channels are private.

I usually donate them to random and personal "black-hole" addresses.
That way, the attackers' funds might help the trading price by decreasing the supply a bit. I'm not receiving/producing a lot of dust anyways.

Rather than a wallet, use blockexplorers that display human-readable format from OP_return data
Like: live.blockcypher.com/btc/ (displayed above) or blockstream.info when you expand "details".

There are wallets that will let you choose a blockexplorer when 'hotlinking' your TXID online,
Example: Bitcoin Core in "Settings->Option->Display tab" or Electrum though "Tools->Preferences->Transactions tab"

But you know that a different seed phrase will generate a different "@username", if it's new to their server, it will ask you to create a new user.
And Folio claimed in the OP that his friend generated the same wallet username when he restored from the backup seed phrase.

For the BIP39 passphrase, I don't think Coinbase wallet app has an option to enable it;
the PIN however is just an app security feature and I tried to load the same seed phrase with different PIN and both generated the same addresses.

If Folio's friend is telling the truth, this is an issue with Coinbase wallet app itself (I'll take it with a pinch of salt).

Is "Spend only confirmed coins" unchecked?
It's disabled by default and should stay unchecked if you want to use that feature.

Anyways if it's disabled, it should work with the latest versions.
It's either your additional UTXO isn't enough for the new total fee or...
that additional UTXO was sent from the receiver's wallet and it spent the output of the transaction that you're trying to RBF, because you can't use the child as an additional input to the parent.

But I bet it's the former.

In other words, the issue was just a cloudy memory?

Okay, I think you wanted to know why the previous balance was still displayed that time despite being sent to your other wallet.
The reason is: Electrum won't instantly deduct the unconfirmed outgoing transaction from the balance displayed below.
Something like this will be displayed next to the balance instead: "[-0.0xxxxx unconfirmed]", It needs to be confirmed first before actually deducting from the balance.

Plus last month's final week had a bit high average transaction fee IIRC so that Tx should've been sitting in your wallet unconfirmed for a week or two.

Call it an "address", using wallet might mislead others into thinking that you're talking about a wallet software or a wallet file with set of addresses.

Okay, when following HCP's guide, look for that particular address when exporting the WIF private key.
The correct private key should be in the next 2 lines after the address, don't forget to tick "Include Unused (Address Pool)" to display them all.

Have you, by chance stored the "seed phrase" online?
That's the 12-word backup that Electrum instructed you to write during the wallet creation.

Because anyone who has access to it will have access to your wallet whether they know your passphrase, access to your wallet, or not.

Was it a recovered drive or PC? The context sounds like you've forgotten about it.

You can try upgrading your Armory to the latest version, the latest is 0.96.5: https://bitcointalk.org/index.php?topic=5088934.0 | https://btcarmory.com/
Your Bitcoin core is also outdated, the latest is 0.20.0 as written above the forum's menu.

I can't agree more, the name sounds wrong to me for the famous use-case.
Probably because historically, they were used as another form of "mining", an alternative to POW / POS.
Explained better in the Wiki (source): https://en.bitcoin.it/wiki/Proof_of_burn#Introduction_and_motivation

The addresses tab is hidden by default, you can enable it by clicking "View/Visa->Show Addresses".
But since that wallet seems connected and synced, it looks like you've imported the wrong private key or you've sent a "different Bitcoin" to Armory before.

Do you still have the TXID of the inbound transaction?

The "Broken English" alone is suspicious enough, are you sure that you're downloading from the official website?
You can use the stand-alone version that's not required to be installed but I suggest you to use the latest version instead.

By the way, the current download links in the website doesn't have 3.3.4 aside from the "previous releases".

They call those addresses "Proof of Burn" and they can be created by either scripts, tools or online sites like https://gobittest.appspot.com/ProofOfBurn.
As the name implies: "Burn", it means that bitcoins sent into those addresses were practically burned or better "bury" since they were created without knowing the private key.

That link seems to have problem with long prefix, there are Python scripts that's available online that you can use an alternative.
I'll edit this if I found the link.

-Edit-

Here's the Python code (not mine): https://gist.github.com/CoinWhisperer/6d673f1f3d13da1611cd

I can also visit the site without any problem.
Perhaps they've been rejecting your connection because of "bad IP", it happened to me a year ago with my previous ISP.