#Threads is probably the closest one in terms of relevant people to follow, but it has a poorly executed main page, "for you" content is preferred over people you are actually following. The UI is bases on tabs, you tap on one menu/feature etc. in order to switch to the tab you are actually interested in (followers/following, for you/following timeline and so on).
Basically you will find a lot of the people you followed on twitter but the user experience is not polished enough.

#bluesky is the closest alternative to Twitter in terms of user experience and UI, as far as I can remember it looks exactly as Twitter from several years ago. Unfortunately you will not find a lot of active users right now, heads of states etc were banned until recently and most notable accounts are not on the platform.

#mastodon is the coolest alternative in my opinion and the one I really want to thrive. The UI is quite customisable, but the presence of notable accounts is worse than bluesky, for now at least, I cannot wait on full threads integration to have the best of both worlds.