118.0.2 (64) linuxmint flatpak

Open firefox browser in fullscreen mode 1830721 - firefox nightly fullscreen has borders around all sides when using userChrome.css -moz-appearance,release version has not. 1830681 - Fullscreen mode has padding, doesn't occupy the whole screen 118.0.2 (64) linuxmint flatpak its in the pref.js that i added https://github.com/arkenfox/user.js but slightly edited. EDIT: went to Arkenfox/user.js github to troubleshoot