Actually, I remember half of the password, so I downloaded btc-qt v0.21.0 and loaded the wallet and, initially, there was no problem and I loaded it without errors. Indeed, the wallet is encrypted.
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I still find it very strange that I do not get the btc key but I do with the other currencies / versions ...
Why is it strange? ...
I still find it very strange that I do not get the btc key but I do with the other currencies / versions ...
How do you even know that the "half of the password" is actually correct? Are you assuming that because the "half of the password" worked on some of your other wallets (for ltc/doge etc), that it must also be "half of the password" to your btc wallet? Unfortunately, you have not way of knowing this is true until you actually find the correct passphrase for the wallet.dat.
It is entirely possible that the "half of the password" that you believe to be correct, is in fact completely wrong... which would explain why btcrecover is not able to recover the complete passphrase, as if you've given it an incorrect starting point, then btcrecover will never be able to find the passphrase.
That is to say... if the passphrase is: password123
and you believe that the passphrase starts: "abc", then there is literally 0% chance that btcrecover would be able to get end up finding "password123"