> it needs two (!) DisplayPort cables on a GPU with MST support, meaning that in practice, it only works with nVidia graphics cards.

This is nonsense, of course AMD graphics cards support MST. https://www.reddit.com/user/hubsdocks/comments/rcf6vz/dell_w... Perhaps some weird Linux driver limitation...?

As for DisplayPort, the only semi-modern customer grade video card with four DisplayPorts is the AMD Radeon™ RX 5700 XT Taichi X 8G OC+ RX5700XT TCX 8GP.