I have some older Zotac boxes that have the NVidia ION video chipset, which is not supported in newer Ubuntu releases. The boxes have been great frontends, and I really don't see the need to replace them, but have to upgrade the OS from 11.04 (Natty) to 22.04 (Jammy) in order to intall the latest MythTV (I've gone with 22.04 since it's an LTS releae)
I've researched and found a PPA that supports this older chipset.
The ppa is kelebek333/nvidia-legacy Site
I've used this on XUbuntu, LUbuntu, and Vanilla Ubuntu with no issues, and it allows me to use the VDPAU playback settings in MythTV.
From a shell prompt:
sudo add-apt-repository ppa:kelebek333/nvidia-legacy
sudo apt install nvidia-340-updates nvidia-340-updates-dev xorg-modulepath-fixReboot the system. (That should be it.)