The mixed-list warning named the wrong mechanism. Old names mostly still
resolve on 24.04, because each renamed package declares Provides: its
unsuffixed name. The exception is libasound2, which liboss4-salsa-asound2
in universe also claims — apt refuses to choose between two providers and
aborts the whole install line rather than silently installing a shim.
Also pins libfuse2t64 as definite rather than possible, and widens the
libfuse2 line to cover 20.04, which is in the support matrix.