Quoting Stefan Krusche <linux@...>:
>
> I'm using trinity 14.0.5 from preliminary stable builds on devuan  
> ascii (debian stretch).
>
> Through the most recent upgrade, that I executed on 2018-07-02 11:42:01, tdm
> (amongst a couple others) got upgraded:
>
> tdm-trinity:amd64 (4:14.0.5~pre39-0debian9.0.0+6, 4:14.0.5~pre42-0debi
> an9.0.0+6)
>
> After this upgrade tdm wouldn't start anymore and in /var/log/boot I  
> found this error message:
>
> Not starting Trinity Display Manager (tdm); it is not the default display
> manager.
>
> The file is there:
> $ ls -l /etc/X11/default-display-manager
> -rw-r--r-- 1 root root 14 Jul  2 11:42 /etc/X11/default-display-manager
>
> And it says:
> $ cat /etc/X11/default-display-manager
> /usr/bin/slim
>
> Solution:
>
> $ dpkg-reconfigure tdm-trinity
>
> Of course, tdm was the default display manager already before the  
> upgrade, and,
> as you can guess from the above, slim is installed, too.
>
> I think, it should not be necessary to reconfigure the display manager, or,
> least, the user should be prompted to do so at installation.
>
> IIRC, this happened already at the previous upgrade to ~pre39.
>
> Has anybody seen this? Do you think it is a bug?

FWIW, I've seen this a time or two in Trinity 3.5.13 -- PSB.

Jonesy