I jave no problem with Firefox, it’s syncing everything between desktop/mobile, addons you are using everyday, it’s possible to add some addons from desktop version to mobile, possible to sync on your server, and to make your own addons collection to share betweens mobiles on your account.
Just find some informations on doc about how to make your collection, and you’re fine with that. It’s working like that since many years. After finding this, I’ve forgot completely Brave on mobile.