Just to update, this technically isn't necessary for Waydroid to work. https://github.com/choff/anbox-modules exists which allows installing binder (and ashmem, so as previously said, not needed anymore) with dkms. I have it working here https://build.opensuse.org/project/show/home:llyyr:Waydroid in case anyone wants to try, I intend to submit it to Factory soonish once I clean up the spec files and stuff. Note that it won't work without setting psi=1 in your kernel config, because Android's lmkd requires it.