It's open source. GrapeneOS is based on AndroidOS without Google's tentacles. Tor Browser is a modified version of FireFox LibreWolf is anothet great privacy-first fork of FF. There's no need to bounce from FF forks. I haven't used their main browser as a daily driver for years. Maybe soon we will finally get GraphenOS Vanadium for desktop. It is by far the best browser for privacy and security on mobile.