I'd say you should focus on getting the right derivation path first, then wallet file recovery as a last resort.
Yeah, absolutely. Just how.......?
With the modified tool of iancolman.io that @HCP had posted, I've been trying & until now no result. Seems I'm trying wrong. Any tip on that?
What was the electrum version bundled with Tails before you updated to version 3.3.8? Since you mentioned that the seed restores the wallet fine on the old version, but it restores to a different wallet on this newer version, it is possible that Electrum has changed the default derivation path or otherwise the algorithm it uses to derive the private keys, hence why knowing the old electrum version (or at least the Tails version you used and we use package manager repositories to pinpoint the Electrum version ourselves) is so important, as it will allow us to scan for code changes on Github related to key derivation.
Edit:
Do you at least know which version of Tails you used at the time?
Tails version: 3.16.
Electrum version: I sent an e-mail to Tails support team, hopefully they will reply because they know the answer.
If not, then when I'm right it was 3.3.4 - might be also prior to this one
I have used this instructions to download the appimage so that I update the Electrum software manually:
https://electrum.readthedocs.io/en/latest/tails.html because the wallet had issues getting online
But 3.3.4 that problem was fixed - so seems like I have used the wallet prior to 3.3.4 - but as I said, I am not certain.