Totally agree with the poster, its like Apple are being monopolistic and forcing devs to update.

We are getting the exact same error it is a nightmare! Are we really being forced by Apple to update to Xcode 12 or they won't accept our apps to Testflight etc ? In our case we are using Xcode 11 and had no issues up until yesterday. Now our attempts to submit to Testflight are being met with this error.