@poster No, I have always been on 64bit.
But, just this very moment I can provide an update how I got it to work!
Since I regularly do system backups, I just tried, what happens, if I restore my C-Drive to the December 2025 backup. I could make MusicBrainz work, again!
The installed MP3Tag Version at that date was 3.30.
Then I installed V3.32, that @Florian had provided: MusicBrainz produced the https error, again.
From my backup, I could restore the V3.30 program folder: no more https-errors.
So, there must have been a change between V3.30 and V3.32, that causes that https-error on my old WHS2011 system.
I will now restore my C-Drive back to the current backup, and then just try to get it working with V3.30 of MP3Tag.
@Florian If you would like to do me a big favour, could you please provide me with the 64bit downloads of 3.30 and 3.31? I will happily try to install those and give feedback about the outcome. Maybe, this helps other users with older systems, as well...
P.S.: I'm a step further - there is a musicbrainz.src configuration file in the data/sources subfolder. Even if I update MP3Tag to the current V3.35 of MP3Tag and replace its musicbrainz configuration file with the one from V3.30, then I don't get https errors.
I don't know, what changes have been made, and if I can use that old configuration file with the current version without causing errors, though. Just thougt, I'd mention that...