I found a work around for this problem. The work around is to use Apples Transporter App. You can download this APP on you Mac from the App store. Create your ipa file by using the Distribute App in the archive section of Xcode and then use the Export option. This will create a folder wherever you want it located which has the ipa file Transporter needs. Xcode 12.3 still has a problem, as of Dec. 22, 2020, not letting us upload (Distribute App) directly from Xcode to the App Store Connect.

I too am new to this. I found the book "Beginning iOS13 & Swift App Development" very useful and it helped me get my first two Apps developed. The author is Greg Lim and he also replies to email questions you might have. Very helpful. He has a new book called "Beginning iOS14 & Swift App Development" I'm starting to read and it looks just as good. BoatCaptainQ