Intel, and modern AMD. So really it's just nVidia.

I've been using the default open source drivers on my ThinkPad at work with Nvidia gpu and never had a problem with multiple screens etc.

It really is propriety drivers that's the problem

You are likely not even using the nvidia gpu or the driver (nouveau) if your thinkpad is new. Or you are using just the nvidia gpu if you have discrete mode. For older designs with weird wiring and optimus, nouveau is very problematic for even basic use with external screens. Problems range from screen tearing (reverse prime, no solution), stability, poor performance, and fundamental usability issues such as screen not coming back on after suspend. Not that this is nouveau's fault, for it is a reverse engineered driver afterall.

Sounds like my experience with AMD Vega from my Thinkpad A485... its a nightmare, using ubuntu and amdpro or mainline kernel...

AMD should, in theory, be quite good these days, especially with a new kernel. Note that amdpro drivers are generally not recommended despite the word pro in them. The newer amd drivers are all free and being merged upstream continuously. pro (afaik) is the older proprietary driver with specific optimisations for things like CAD, but otherwise doesn't have much use these days.

D'oh! That's what I meant to say.

These days I use AMD, and I just haven't had to think about it. Before this I had Nvidea, and even there the open drivers were fine until I wanted to play games.

>Intel works flawlessly

Kernel DRI drivers, yeah sure. Xorg's xf86-video-intel is a buggy pile of shit that hasn't seen a stable release in 5 years.

Currently the best you get on linux with intel is modesetting driver with glamor for 2daccel. Or use wayland, I guess...