I have dual monitors and it works fine for me, so it is hard for me to debug your situation.

Gossip rests on top of egui/eframe which uses winit which handles windowing.  We don't mess with windowing code, we just utilize the libraries provided.  It sounds like the problem you are experiencing might be at the winit level, so if I were you I would start reading through the issues on the https://github.com/rust-windowing/winit repository and maybe you'll find something.  If you find something that requires a change to gossip code, let me know so I can fix it for everybody.

Also, you might have a window manager issue, or a display driver issue.  I've personally had a similar experience when using linux with an nvidia card in a laptop against two monitors, and I solved it by installing the nvidia drivers.