Am Sonntag, 15. Juli 2018 schrieb Nick Koretsky:
> Um, no. This 99% not trinity bug. Your test result indicate bug in
> either in dpkg or debconf, and considering i dont have this problem on
> debian stretch it is probably a devuan introduced bug.

I think I misunderstood your previous mail on 04.07.2018 from which I concluded 
after I did the testing that it is a bug in tdm-trinity install scripts.

> If it changed to slim - Force reinstall slim.
>
> If default dm remained slim after that than this is a bug in tdm-trinity
> install scripts, create a bug report in trinity bugzilla.
That is what happened in all my tests.

> If it changed back to tdm-trinity 
That happened in none of my tests.

Also I found an old bug report (#36) on trinity bugzilla[1] which described the 
same problem with gdm and kdm-kde3 packages and which had been closed "due to 
lack of response". That assured me somehow of having run into the same one.

> than this is a bug in dpkg (probably devuan one, as i dont have this problem
> on stretch). Report this to devuan.
The slim package has been adopted by devuan. After all, I think you're right. 
Thanks again.

Kind regards,
Stefan

[1] https://bugs.trinitydesktop.org/show_bug.cgi?id=36#c0