Not sure whether it can fix the font problem, but in general Flatseal allows you to customise permissions for installed flatpaks.

https://flathub.org/apps/com.github.tchx84.Flatseal

Just started using the Inter Display fonts and IBM Plex Mono fonts for my GNOME desktop.

https://github.com/rsms/inter

https://github.com/IBM/plex

Both are packaged in Debian.

There is even a discussion about making Inter the default font for GNOME: https://gitlab.gnome.org/GNOME/gsettings-desktop-schemas/-/issues/52

Pika Backup is another user-friendly Borgbackup GUI.

https://apps.gnome.org/en-GB/app/org.gnome.World.PikaBackup/