Yesterday I installed Kubuntu 20.04 from scratch on a Lenovo Thinkpad T490 laptop with a GeForce MX250 discrete graphics adapter.
Prime render offloading fails with:
$ __NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia glxgears
X Error of failed request: BadValue (integer parameter out of range for operation)
Major opcode of failed request: 152 (GLX)
Minor opcode of failed request: 3 (X_GLXCreateContext)
Value in failed request: 0x0
Serial number of failed request: 25
Current serial number in output stream: 26
This was working perfectly in 19.10 on the same machine, using xserver-xorg-core version 2:1.20.5+git20191008-0ubuntu1.
How is Prime render offloading supposed to work in Ubuntu 20.04?