I think that maybe your system was not upgraded and you're still using the
same package versions, but your sources.list file (the one the system looks
at to know where to get its packages) has been incorrectly switched to the
Flidas one.
To check if this is the case, I would look at the contents of this file (you
can do that easily on the terminal with sudo nano /etc/apt/sources.list ) and
if it's showing flidas entries, I would try to switch them back to belenos
and running sudo apt-get update again. If it says that nothing or almost
nothing is to be installed, you would be good to go (or at least still have a
perfectly working Trisquel 7 install with your audio setup intact, just like
it was before attempting the upgrade).
This could happen because in the process of dist-upgrading, this substitution
is made at an early point; when something goes bad, this change should be
undone, but maybe something went really, really bad and the rollback didn't
work.
Anyway, please try that (if it doesn't work, you can just set those entries
back to their current value) and tell us about the result.
