For reasons that I won’t go into here, I switched my desktop computer from an X.Org session to Wayland. One thing that didn’t work was my customised trackball button mapping. That was never particularly user-friendly under X.org, but under Wayland it’s not supported at all. Or rather, it’s delegated to the desktop environment, and as I’m using Gnome, there’s scant customisation available.
But that doesn’t mean we’re out of luck.