Comment # 4 on bug 1225296 from Stefan Dirsch

Ok. Your gfx card was released in 2009. The latest proprietary driver still
supporting it is 340.108, which is End-Of-Life since a long time now. It's
more-or-less impossible to get this driver still building against Kernel 6.4 of
Leap 15.6.

I'm afraid you need to rely on nouveau kernel driver.