Flatpak on Raspberry Pi aarch64, glitched window, no full screen

When running the flatpak version on a Raspberry Pi (CM4), under 64-bit Raspberry Pi OS, Retroarch starts up in a weird tiny window with two title bars.


You can click the maximize widget, but it only takes up about two thirds of the desktop, with a big gap above it.

If you run the flatpak with "-f" for full-screen, it goes through the motions of starting up, but then immediately quits. There are no errors in the log, if you also specify -v.

[log.log](https://github.com/user-attachments/files/16300906/log.log)

Start by reviewing the attached log.log and reproducing the Flatpak launch on a Raspberry Pi CM4 with 64-bit Raspberry Pi OS, first normally and then with -f and -v. Done means RetroArch opens with one correctly sized window, maximizes across the desktop, and does not quit when launched fullscreen.

Written by the indexing model from the issue text.