Thanks for explaining!
I booted Trisquel 6 in live mode from a CD, to compare things with Trisquel
7. The same xserver-xorg-video-* packages were installed (but perhaps using
different versions; I didn’t check that). `/etc/modprobe.d/` includes the
same files with the same contents. `/etc/X11/xorg.conf{,vesa}` seemed
identical too. So none of the things to try that I’ve found when
researching—removing packages, blacklisting modules and editing
xorg.conf—should make any difference.
My guess is that it just _happened_ to work for me in Trisquel 6. Something
probably got updated in Trisquel 7 that now detects my graphics card.
In the end I decided to go back to Trisquel 6. I’ll use that until I feel
like getting a new computer.
(I actually had more problems with Trisquel 7, which contributed to this
decision: gnome-panel took a long time to appear, running for example `rm
somefile` or `gvim .` printed warings or errors, and while upgrading I got a
message saying that 'initramfs-tools' couldn’t be installed. But this is
off-topic. Just noting. After a few days of trying to fix things I got tired
of it, and needed a working computer again.)
