The new 'test' if you like wallet was created using the bitcoin core 22.0 bitcoin-qt GUI by choosing create wallet with encrypt wallet and otherwise default options except I chose make blank wallet. I did however add a number of private keys after this using the importprivkey command from the console and choosing window receiving addresses from the GUI shows 9 addresses.

I am trying to recover any possible bitcoin wallets by scanning my hard drive which may contain or did contain backups e.g. raw disk images of hard drives I used to run bitcoin a long time ago (around 2010).

I may also have the physical HDDs still but I don't have time to examine them now and thought I'd go for the easier option of downloading pywallet and using the recover option to scan my current hard drive.

I ran
sudo ./pywallet.py --recover_size=3666Go --recov_device  /dev/dm-3 --recov_outputdir /home/myusername/recovered_wallets

Which gave the output
'Found 3 possible wallets
Found 0 possible encrypted keys
Found 0 possible unencrypted keys
The wallet is encrypted and the passphrase is correct

Importing:

The new wallet /home/myusername/recovered_wallets/recovered_wallet_somenumber.dat contains the 0 recovered key'

The hard drive as well as containing old backups also contains a current installation of bitcoin-core-22.0 and the associated wallet.dat so I would expect pywallet to find this and that at least one of the three would be this one.

However when I do
sudo ./pywallet.py --recover_size=3666Go --recov_device  PartialRecoveryFile:/home/myusername/recovered_wallets/pywallet_partial_recovery_somenumber.json --recov_outputdir /home/myusername/recovered_wallets

and use the known wallet passphrase for the new bitcoin-core wallet (the password I use to unlock my wallet from the console window of bitcoin-qt of bitcoin-22.0 by walletpassphrase) it shows the same followed by

Possible wallet #1
     with passphrase #1

Etc.
And still

Importing:

The new wallet ... contains the 0 recovered key'

So I would like to know if these wallets are actual wallets or not (at least one of them should be!) and if so how to find and use them.

I thought maybe to find the files from the partial recovery JSON file so I can maybe know if they are interesting or not?

Many thanks.

I have also taken the generated recovered wallet and after moving the original wallet.dat to a safe place (it doesn't contain any coins anyway now) I replaced it with the recovered wallet. However on attempting to load the wallet it gives the error message  'Wallet loading failed: Unable to generate initial keys' I'm guessing because there arent any keys there.

P.s. I am using fedora Linux 35 and bitcoin-22.0 full (unpruned) node.