First off: don't worry. This is more a sad joke than anything else.

I'm updating a computer running Debian (long story, but I will be upgrading
it to Devuan at some point). When I try installing timidity, apt kindly
informs me of the following:

     serious bugs of timidity (2.14.0-8.3+b1) <Outstanding>
      b1 - #1039396 - timidity: ships sysv-init script without systemd unit

...and that's it. That would appear to be the full extent of the "serious
bug" which jeopardises the entire upgrade.

Another sign of how hard systemd is being pushed, I suppose.

- Antoine