generica is a user on octodon.social. You can follow them or interact with them if you have an account anywhere in the fediverse.
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You can use your phone number with messenger instead but doubt anyone trusts fb enough for that. Signal is good but hard to get others on board.
@generica Yes, Messenger is tied to my phone # only at this point. Unfortunately it's the only way for me to keep in touch with certain family, and no way would they move to Signal.