A nice solution is a domain which only job is to translate everything to the right instance (most popular). Like lemmyweb.xyz lemmyweb.org lemmyweb.etc (many domains owned by different ONG with the same “script” so there is no one single point of failure). The first time you login to this domain you select your user / pass and instance. And then it’s all automatic. I don’t know if what I’m saying has any sense.
Whatsapp imo of better. They are both stealing your data, at least with WA you avoid third parties.
By the way, people answering Signal or Matrix: you really suck big time. Of course that’s better, but it you ever have a friend outside privacy nich (or at all - your momma doesn’t count-) , you would learn that’s not a choice