I’m using arch btw, with KDE and wayland. Posting this incase anyone else is having similar problems.

Some commands that relied on wl-copy like pass -c would return empty pastes.

My guess is that the xdg-mime query (from xdg-utils) returns empty output on KDE, and that wl-copy relies on this to determine the MIME type of piped data, and when it gets nothing back, the clipboard MIME type is corrupted.

The fix was replacing wl-clipboard with wl-clipboard-rs which is a rust re-implementation of wl-copy/wl-paste that doesn’t depend on xdg-mime for MIME detection.