Mesa was the only for a while. (You need libgbm and a DRM+KMS driver to make a compositor and/or EGL_WL_bind_wayland_display for an embedded one). So that only worked with Intel and AMD GPUs. Nvidia now has EGLDevice and EGLStream for their drivers, and they provided patches for Weston and GNOME has added support as well.

does this mean that every compositor has to add gpu support on its own? a gpu that works in gnome would not neccesserily work in sway or orbment?

In the case of NVIDIA, yes. Their GPUs need compositor support and the GNOME people ended up giving in and merging their patches.

facepalm...

It does, but not as you would expect. Last time I tried with an ATI, I had random freezes. But it was a year ago. There were lots of improvements since then.

well, last week i tried with an nvdidia gpu on my workstation and it didn't boot at all.

I'm using Wayland on Arch with and AMD card. It seems pretty stable. Most issues I run into are XWayland issues when trying to run X11 applications.