The Simple DirectMedia Library that is widely-used by many cross-platform games and part of the Steam Runtime now has better support for handling more mouse button events under Wayland.
Last week was a bug report over supporting more mouse buttons than five. While some mice end up binding their extra mouse buttons to keyboard keys, some mice such as when configured via Libratbag+Piper can map them to higher key press input event codes. Theoretically, allowing up to 48 key press input events in total.
Iirc, that was an issue a friend if mine had when wanting to switch. He’s one of those MMO guys who users mice with dozens of buttons, so it’s pretty essential. I wonder if this will help?