Tim is a user on octodon.social. You can follow them or interact with them if you have an account anywhere in the fediverse.
If you don't, you can sign up here.
If you sign up via an instance does that give you a global log in/username?
@princessfluffy Pretty sure the other instances don't even know you exist until you respond to / interact with a user from that instance.
@oneoffsuit You can view all instanced in the federated timeline.
@timvb @oneoffsuit Federated timeline is more like a "friends of friends" feed. It's everyone on your instance, plus all of their follows.