On the whole, I think TestFlight just isn't worth it and it is unfeasable for any "normal" company to use -- I mean, how much control of your internal development process do you want to lose to a third party?

The "drops Wi-Fi connection randomly" issue has been there since at least iOS 13, but I have a new "Wi-Fi connection is extremely slow" issue all the time even when sitting right next to my router and all other devices are working fine. It's almost as if some networking related task is blocking the entire OS and apps (they freeze when trying to do anything network related).

Yep, just encountered this and this is, like so many other things since the post Steve Jobs era, absolutely crazy. A file copy operation without ANY kind of progress indicator. Seriously? And then, no "Copy" or any other options in the right-click menu... you HAVE to use Drag 'n Drop!!!

Same problem here (in my case, for a gapless music player app, where two AVAudioPlayers briefly overlap). This doesn't seem to be possible according to some Apple doc I've read the other day. Only one instance of any kind of player can ever play through AirPlay.

Unfortunately I can't help you, but just as consolation -- I have pulled my hair out over exactly the same problem for a few hours in my game. It's pretty hilarious now that devices have no hardware controls anymore, which is bad enough, the SOFTWARE controls are now so "overloaded" and unpredictable that they essentially are useless, too.

This whole thing is pretty stupid in general. I mean, in 99% of cases, it's completely obvious why an app wants to access the camera. This should be optional at best. The world survived for at least a decade before this requirement surfaced.

Just wait until you're trying to implement a simple file selector ("Document Picker" in Apple parlance). The Apple documentation for it sounds like some kind of writeup on how to calibrate rocket engines, with words I've never heard and incredibly convoluted ways to deal with the file if it's returned. It also doesn't help that all examples on the net for anything are now for Swift, after I had barely learned Objective-C. So am I supposed to learn yet another obscure language now or what?

Don't bother, use a hybrid web app development toolkit. Native iOS development is so ridiculously complicated and convoluted that you'll want to die once every 5 minutes. Do yourself a favour and use something like React.

The problem is really very basic, and it's definitely Apple's fault, and Apple these days frankly doesn't seem to have a single UI/UX expert on site. It's the mere fact that App Store Connect lists screenshots by screen size, while Xcode lists the simulators by model. That is some serious UX b_/llsh1t.