DPI scaling of the regular steam GUI can also be wonky if you have different monitors. For example, I mainly use steam on my lower DPI secondary monitor, but it wanted to scale based on my 4k main one. Could be fixed with an override though.

For all the flak they (rightfully!) get, a 1st party open source nvidia driver is in the works.

Altough it’s only the userspace part and it’s not compliant (yet?) to be upstreamed into the kernel. It is still something.