Hey there! Congrats on getting to test out the BETA! From my understanding the beta testing has ended and your phone should have been updated to go back to 6.0.1/Baseband version G930TUVU4APK1. If you are not able to get the phone to be seen via SmartSwitch, you may want to reach out to Samsung's beta support team directly for assistance. You can reach them at firstname.lastname@example.org or 1-800-726-7864 (24 hours / 7 days a week).
Latest update? I didn't think they were releasing anymore.
You will probably need to Odin and then master reset the phone like they said for reverting.