GtkWindow shadow is broken in Epiphany with amdgpu (and possibly noveau?) graphics when website enters accelerated compositing mode
windows_shadow As you can see here, the Web-window opens just normal, with the normal shadow like every other app does, but once the website is completely loaded, the shadow around the Window is broken and only a fat line.
This also happened in 3.28 (and now in 3.30.1). It happens every time. If you need more information please just ask.
Other GTK themes (like Arc) wont fix it.
Edited by Michael Catanzaro