I always have used 2 numbers, a Canadian number and my US number. I've switched sims between my phone and my watch during beta all the time. Since my first beta test which was for the Note9. It has never affected the builds, as when ever there was a new build i would simply put my us number and get the update and vice versa. It only mattered that my phone was unlocked and was a US csc and my location is here in the US at the time of the OTA.
Hello @Jsan5055 ,
We recommend you still leave physical SIM on the device during the Beta Program as we do use the carrier code to allow access to Samsung Members Beta Version. Primary SIM card CSC is the one used to determine if the device can use Samsung Members Beta version as well as FOTA updates.
One UI Beta Team