This is a mount for the Autodarts scoring system by ROBBEL90.
https://cults3d.com/en/3d-model/gadget/steeldart-score-system-wie-autodarts
It has the exact dimensions so aligning everything is fairly easy.
Can be printed on a 220x220 bed, supports are needed (but not much).
Printed parts:
Other Parts needed:
UPDATE:
This one has holes to mount the dartboard adapter: https://www.thingiverse.com/thing:5751643
The author marked this model as their own original creation.