With an account on mofu.one you'll be able to follow people on any Mastodon server and beyond.
Please check joinmastodon.org for open instances. You can join any other instance and follow/message someone from this instance. It's kind of like being able to send email between a hotmail/gmail account. Here's an uninformed primer on Mastodon.
Get rid of FB, IG, birdsite, etc. and join the Fediverse. Why I quit most services that use your data in exchange for their 'free' services and alternative services you can use instead.
Trouble logging in?
Closed instance. Love no ads, chronological timeline, control over your data, toot privacy settings, and so much more (i.e., these cute mastodon mascots).