thanks for posting such a detailed answer.
about the different debian versions: I don't know which one I should try first:
I found debian mac 12.5 netinst https://cdimage.debian.org/debian-cd/current/amd64/bt-cd/ and I'm giving it a try.
Shouldn't that work, I'll try one of the live cds https://cdimage.debian.org/debian-cd/current-live/amd64/bt-hybrid/
I paste the links to check if I have the right version
Incidentally, the data size difference is so surprising: 0.66 GB (debian mac netinst) against 3.17 GB (debian live). Can I have something in between?
I see. Thanks