In case anybody is wondering how to leave the beta, it is not from the Samsung Members app as indicated in several articles, but rather from the One UI beta app. The instructions there indicate that once withdrawn you can revert back to the official software though Smart Switch using the "downgrade" button, but for me I have not been able to downgrade after changing my status to withdrawn, there is no downgrade option. Support told me to wait a day and try again, will see. If anybody has been able to successfully downgrade I'd love to hear how you accomplished this.
There is an article on Sammobile. SmartSwitch is currently not able to revert you back. But it is expected to be updated in the next week or so to allow you to revert back without tripping Knox.
