Decide what to do wrt. Synaptic
synaptic package manager was recently removed from buster: https://tracker.debian.org/news/1037065/synaptic-removed-from-testing/
This is due to a series of RC bug reports:
All of those are mostly about synaptic's failure to work under Wayland. This has to be confirmed, but discussions during the BSP at Mozilla's seemed to indicate we might get synaptic back in testing (in time for buster).
For now, it's getting pulled from sid so that we can build and test the
feature/buster branch; of course it's possible to adapt ASP to use a different package manager, but that might require more than the few minutes just spent implementing the change to
Install synaptic from sid (refs: #16615).
It's been (hopefully temporarily) removed from testing; let's install it
from unstable, at least for the time being.