Initial summary:
[mageia] trinity-tdm installation produces no running display manager from reaching graphical.target

Mageia 7, host gx28c

Startx does produce a normally working TDE session.

Trinity-tdm 14.0.7 installation provides neither /lib/systemd/system/tdm.service as in Debian, nor /usr/lib/systemd/system/tdm.service as in Fedora. Neither does it produce anything I can find that is supposed to enable or start tdm once it's installed - no tdm.service among output of systemctl list-unit-files nor systemctl list-units, and nothing in /etc/rc.d/init.d/. Nothing about TDM shows up in the journal except for "Reached target Graphical Interface".

Installed is libice6-1.0.9-6.mga7. Removing it would remove trinity-tdelibs and trinity-twin among others.

The only display manager choice provided by drakedm is TDM.

There's also this:
# systemctl list-unit-files | grep play
display-manager.service                                        bad

And this:
# exec /opt/trinity/bin/tdm
(a normally working TDM)

I tried copying /lib/systemd/system/tdm.service from Fedora 31 to /usr/lib/systemd/system/, but got init error messages instead of TDM's greeter. I tried copying /lib/systemd/system/tdm.service from Fedora 29 to /usr/lib/systemd/system/, and subsequently TDM started as expected on boot. It allowed a TDE session to be started, but the CPU was first pegged by a combination of artsd 22%, kmix 13% and pulseaudio 61%, which eventually morphed into kmix 93% & pulseaudio 3%.