It was either never fixed or it got re-introduced in iOS 18.x

Almost two years gone and it's still (or more likely again happening. I tried creating new certs and profiles, updating all involved evices. Nothing works! Any chance to get this fixed? Perhaps take a page out of some other mobile OS distributor's book and make it easy?

I'm facing the same - or a similar issue - I don't see uploaded apps on testflight at all. I can see them briefly in appstoreconnect directly after the upload (using transporter) succeeded, but after reloading appstoreconnect a few minutes later, the entry has disappeared again.