Do you have ‘hide read posts’ checked in your profile? That option hides your own posts, too, because naturally you’ve read them.
Considering Meta mines as much data from as many people as possible just to advertise to them and also they can’t even launch Threads in the EU right now because of how aggressively it tracks literally everything about their users and Threads’ only purpose is to gather more data to sell to more people, I think that alone is worth not letting them play.
Memmy’s on the App Store now. It does still have a TestFlight if there are any spots available but the app store’s version is currently up to date.