Though you may have already heard of it before, there were two recent developments on the One UI 4.0 beta programme, which are:
1- The S21 series beta has concluded, and;
2- The Z Flip3 + Z Fold3 beta has started.
What this implies for those on the S21 series beta: The stable release for the S21 series will be made available in the coming month for US and Canada, unless a very major and unexpected issue arises. Meanwhile, you can stay on the beta. Once the stable release is available, you will NOT get an OTA and will have to flash it manually. Files to that end will be made available here. You can also decide to flash the final US release if you enjoy being free of some of Samsung Canada's most illogical restrictions, such as having no eSIM. Files for the final US release will also be made available.
What this implies for prospective Z-series testers: These phones all have the same SoC globally. Yes, this means flashing will be easy. I have checked and files are not available yet and will be sure to upload them and make an announcement as soon as they are. You will have to be a bit more patient, they could be made available anytime from tonight to next week.