Success! I finally noticed a difference between the instructions in the latest Xcode beta release notes and Quinn's instructions:
… remove related profiles from ~/Library/Developer/Xcode/UserData/Provisioning Profiles and ~/Library/MobileDevice/Provisioning Profiles
I had cleaned out that first directory but not the second. Deleting the relevant profiles in both directories seems to have fixed everything.
Topic:
Code Signing
SubTopic:
Entitlements
Tags: