If you used the distro packaged driver, there shouldn’t be any issue with the 470 driver and kernel 6.8. -But- installing kernel 6.8 from some random source on Mint 21 renders the kernel headers package incompatible to the Mint system so the nvidia driver won’t compile. You probably fell back to the fbdev driver in that case.
Mint 22 comes with kernel 6.8, so everything is compatible, the nvidia driver compiles. -but- AFAIK, Mint 22 changed to Wayland per default, so with the 470 nvidia driver, setting kernel parameter nvidia_drm.modeset=1
is needed for graphics to work.