There appears to be a rather major regression in debhelper 1.13.4 and 1.13.4nmu1, which is forcing unit files to go in /usr/lib/systemd/system, instead of /lib/systemd/systemd (where sytemd will actually pay attention to them).
On systems with ursmerge, things should still work, thanks to the compatibility symlink, but this will cause packages with unit files built since debhelper 1.13.4 was released to unstable, or uploaded as source builds, to be incorrect, triggering a Lintian error and breaking on systems that don't have usrmerge installed. For more details and analysis, please see: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=992469 I just wanted to post a warning that if you were planning on building or uploading new source-only uploads to unstable now that Bullseye has been released, and your package contains systemd unit files, you may want to hold off until this bug gets fixed... - Ted