Just added a bracket to @Malolo's screw-less / snap fit Raspberry Pi 3 Model B+ Case & Stands so that I could mount it to the 2020 aluminum extrusion on my Anycubic Kossel Plus. These mounting holes should work for just about any other purpose as well with the right hardware, including 3030 aluminum extrusion or just mounting to pre-drilled holes.

The holes are for M3 screws. If you wish to mount to 2020 extrusion, then you will need 2x M3 x 6mm screws and 2x 2020 Series M3 T-Slot nuts.

This design just modifies the bottom of the case. You will also need to print any one of the case tops from the original model here.

The OpenSCAD source used to add the brackets is also attached, so the mounting points can be customized if desired.