@mcc@mastodon.social @LaurentB45@mamot.fr Depends on how you installed Firefox.

a)A default Mint install has a Firefox deb package pre-installed. This is packaged by the Mint team (it's not from Ubuntu or Debian, unlike the majority of Mint's deb packages). You can update this manually through sudo apt upgrade, or through the GUI using Mint Update. Mint Update also allows you to configure automatic updates.

b)If you replace the deb Firefox with a flatpak, then the default settings on Mint will update it automatically when you boot (this can be changed). Flatpaks can also be updated through Mint Update, or manually through the CLI.