Update: Got this to work by creating the archive on my teammate's computer. He's running XCode 12.0.1 while I'm using 12.2. I then airdropped the archive to my computer and it showed up in the organizer and things went smoothly from there. I assume this an issue with the latest XCode.

Also running into this on XCode 12.2. I moved XCode.app to my trash, shut down and started my computer again, and reinstalled XCode but my archives still aren't showing in the organizer. Because of this I can't submit my app to the app store. Maybe relevant: When I double click on the archive at ~/Library/Developer/Xcode/Archives/2020-11-16/myarchive.xcarchive it opens XCode with the alert "The archive could not be installed." / "The archive may be corrupt or unreadable." When I check the package contents of this app versus a previous one, I see it only has Products, dSYMs, and BCSymbolMaps directories while the old one also has an Info.plist and SwiftSupport and SCMBlueprint directories. I've looked at the advice here but my project was already set up correctly: https://developer.apple.com/library/archive/technotes/tn2215/_index.html#//apple_ref/doc/uid/DTS40011221-CH1-XCODE_SUCCESSFULLY_ARCHIVED_MY_APPLICATION__BUT_THE_ARCHIVES_ORGANIZER_DOES_NOT_LIST_MY_ARCHIVE