@firstname.lastname@example.org it is supposed to work on #android, but i can't confirm that...
i'm using #orfox and #fossbrowser, which however do not support sync.
there is no pure #firefox in the @fdroidorg repository (and #google #play #store is not an option). just tried #icecat but cannot sign in to sync (probably related to https://savannah.gnu.org/bugs/?50960)
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