Honestly anything that doesn’t get ported to wayland is probably old enough that it doesn’t really make sense to use as your primary desktop anyway. The most niche DE I regularly use is NsCDE, but it’s entirely FVWM scripts and FVWM is planning on adding wayland support. It’ll be a little sad to lose things like Trinity, WindowMaker, and Afterstep, but they were never amazing anyway and either way I doubt X will actually be unusable for a long time still.