Please tell me more about your window environment; Gnome/Mutter don’t support Client Side Decoration (CSD) for Wayland clients, so wezterm draws its own limited decorations. Those don’t support right clicking or context menus, so I’m not sure how that maximize menu you described shows up.

Sure, though I don’t yet know anything beyond ”this is a standard Ubuntu 20.04 (Gnome) desktop, using Wayland”. Are there any commands I could run to find out more?

Copy & paste doesn’t work in the debug overlay (any selection I make is deselected as soon as I hit Ctrl), but there’s nothing there anyway apart from the intro (no matter how many times I trigger the resizing issue).