I'm not sure an open source Nvidia driver is necessary for this. The problem mostly seems to be that Nvidia does not support standard interfaces all other open

I'm not sure an open source Nvidia driver is necessary for this. The problem mostly seems to be that Nvidia does not support standard interfaces all other open source and closed source drivers support. Nvidia was very late to the party to support kernel modesetting, which is supported by all other modern graphics drivers. Nvidia refuses to support GBM, a standard way of allocating memory for graphics. Either they refuse this out of spite, or (more likely) because it fundamentally doesn't fit the architecture of their closed source driver. They are so desperate to push their alternative, EGLStreams, that they have lobbied Gnome and even created patches for KDE to be able to run Wayland on these DEs. This is not some closed source vs open source thing, since AFAICT the closed source Mali driver seems to support GBM and Wayland implementations that need it. Therefore, the problem isn't that Sway doesn't support Nvidia. The problem is that that Nvidia doesn't support the standard ways to do graphics on Linux. This something Nvidia can in principle remediate themselves if they want it enough.