I'll throw in my 2 cents. Maybe it will be helpful for someone. I have Morphos, Leopard and Debian 11 triple booted in my G4. In the agp slot I installed Radeon HD 3450 for Debian (full 2d and 3d) and MorphOS (only 2d, waiting for new drivers ;) and in the pci slot GeForce2mx400 with dual bios pc/mac(!) (of course for OSX, works on Debian too, but without 3d).