Dear Maintainer,
Since sonic-pi-server makes symbolic links to some subdirectories in
/usr/lib/erlang/lib directory for its Tau server, it is bound to break
on every upstream release of Erlang.
Currently, it is broken in unstable, and only autopkgtests prevent Erlang
29.0.3 to migrate to testing, which would cause breackage there.
I suggest to make the dependencies of sonic-pi-server on erlang-base
more strict, and add an upper limit of the required version (it looks
like erlang-base (<< 1:29.0.3+dfsg+) with added "+" at the end, see the
attached patch for the detail). And since erlang-depends does not
provide such a limit automatically (it seems to be a fairly unusual
requirement, all the other packages happily work with the newer
Erlang versions), I've constructed it in debian/rules using grep-status
from the dctrl-tools package) in the patch.
After that, sonic-pi will still require binary-only NMU to adapt to
the new Erlang version, but at least it will not break any existing
installation in unstable (Erlang packages will refuse to be upgraded
for those with sonic-pi-server installed).
If it is okay to you and you approve the patch, I can do NMU to
incorporate it.