It’s true that Waydroid may not/probably doesn’t work on X/Xc, but I haven’t heard of anyone confirming yet, (I did confirm that the kernel is not able to handle lxc, but not sure if it’s the same) - would be great if you try and report …
As far as the install problem, did you try this
From here - https://github.com/sailfishos-open/waydroid ?