I was able to upload a build to TestFlight this morning (CET), but since then the builds have not shown up

Same here, duplicate error when uploading again, but no sign of the build anywhere in App Store Connect

I have the "App Uses Non-Exempt Encryption" in my info.plist and I still have this issue

Same issue here. After updating to XCode 12 yesterday, my build is not showing up in App Store Connect. Also getting redundant errors if I try uploading again.