Im joining in on the reddit ditching thing, and was kinda worried at first that i wouldnt be able to like use it the way i did reddit as it feels like a whole new place, but after engaging with posts and people and actually being a part of lemmy rather than being lurk mode all the time i was pleasantly surprised with how easy it is to become a member of the community, theres a reasonable amount of subs (or whatever the other word for em is) that fit my interests, enough linux content and shitposting for my liking, and the overall random posts made by people equally fed up with Leddit. (also i admit i used reddit a little cus there was this post on the fedora sub showing how to fix a sound issue i been having after a recent update)
You can definitely interact with Lemmy from a Mastodon account, I’ve seen various people demoing it over the last few days and I’ve followed a couple of smaller communities here so they show up in my Mastodon feed. That said it’s not the best interface for reading long posts.
I’ve seen people from friendica too, I just wish there was a way to view mastodon and other non Lemmy posts that weren’t connected to lemmy directly, as is if I view a mastodon account for example I only see what they’ve posted to lemmy unless I look from a mastodon account