I'm quite happy with my previous mATX Open Frame Case, with the exception that cutting, drilling and tapping the 2020 extrusion is a chore. This design is fully 3D printed and fits on a single 200x200 or 250x250 build plate.
It should be compatible with any Micro-ATX motherboard and SFX PSU. The ones in the photo are:
Required hardware:

Parts are designed with a 0.6 mm nozzle and 0.3 layer height in mind. I've had good results printing in PLA with 3 perimeters, 4 top and bottom layers and 20% infill.
Note that in the 200x200 version, the back part of the frame is split into two parts that require an additional M3x16 socket heat bolt and M3 nut.
Many thanks to the authors of these models:
The author marked this model as their own original creation.