Comment by Arnavion
I actually went looking at the source code to see if this would work on Wayland and it doesn't. The clipboard snooping is implemented by listening for events using gdk.Clipboard, which is not an ext_data_control_v1 implementation. So on Wayland it'll only notice clipboard events if it's in focus (or if the compositor sends clipboard events to unfocused windows, which I'm not sure any do).
https://github.com/murat-cileli/clyp/blob/2c0ce6c33813c3f35f...
Edit: Yes, tested it now and it doesn't detect clipboard events from Wayland windows when it doesn't have focus. It only detects events from Xwayland windows when unfocused, or if I copy something from a Wayland window and then focus the clyp window then it detects the thing I copied.
It's almost as if a Wayland compositor should keep a list of trusted apps to broadcast clipboard events to, somehow similar to how screenshots are handled. (Not that Wayland is well-rounded in this regard.)