I’m using 20.04 and a Wayland session. My preferred focus mode is to have it follow the mouse cursor:

$ gsettings get org.gnome.desktop.wm.preferences focus-mode
’mouse’

Unfortunately this causes GTK apps’ popup (RMB) menu to jump to the app window corner when opened. I’m attaching a screencast, where I demonstrate the bug first, then reset focus-mode to ’click’ to demonstrate the bug no longer manifesting. (Please excuse the flashing. It’s just a video artefact caused by Gnome’s built in screen recorder, which was the only one that at least somewhat worked.)

This has been reported upstream, where a fix was recently merged: https://gitlab.gnome.org/GNOME/mutter/issues/1103