I am on a fresh install of Fedora: only upgraded all packages after install, installed nvidia driver and ffmpeg from rpmfusion.
Libadwaita flatpak applications (like Extensions Manager) have an unwanted border around them (see below).
The problem only occurs with both X11 and NVIDIA driver.
I tested it with all other combinations (X11, nouveau), (Wayland, NVIDIA), (Wayland, nouveau) but the problem does not appear there.
Any idea on how to fix this issue?