EndeavourOS is moving to KDE Plasma for its live environment and offline installer from Xfce. You’ll hear no complaints from me!
Will that make it more usable for nvidia users?
Don’t bet on it. For a while NVidia had hired a guy to implement EGLStreams support in KWin and other issues around supporting the Nvidia driver but since a year he’s gone: https://invent.kde.org/users/ekurzinger/activity
Since then they’ve made their driver open source.
No, they didn’t. They open sourced the kernel module interfacing with the actual driver that’s in user space. The actual OpenGL, Vulkan, etc. implementations are all closed source.