Incidentally, I've updated my bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=2249379
The problem appears to be wayland, I thought I had tested under
x11 and wayland, but gnome was sneaking a wayland session
into existence behind my back. When I really managed to start
in x11 for sure, emacs no longer seemed wacky.