I'm at work and just checked my home system and I see that limit too.That just means you can't create an app that can't be installed on anything less than iOS 13.3 though.If you need that it is of course a problem, but it does support running and debugging on iOS 13.3 devices.I am able to select and run my app on an iOS 13.3 simulator as well.

I would imagine that you should contact Square to see what is involved and if they support third party software using their hardware.

You can with limits...https://developer.apple.com/support/enrollment/There is a FAQ near the bottom that addresses it.I had the impression that device certificates have to be renewed on something like a weekly basis, but I've not used the free program myself.

I wouldn't expect it to be possible without jailbreaking the device since that would be a significant privacy issue if third party apps could access a user's mail.

Did you try the usual quit xcode and restart it?It might also be worth rebooting your mac.

I worded that poorly.I was able to build and run on my iOS 13.3 iPhone.

Xcode 11.3.1 from the mac app store supports the release version of iOS 13.3.At least in terms of being able to build to it.