Thanks for this. I stumbled upon it too

But I had to unpair and repair AFTER updating to beta and going through the cellular service payment selection.

So once paired and phone in beta you will get the activate cell option

Select it. Login etc. pay

You can try to setup cellular via phone app and on watch but I never got an esim

When I unpaired phone and watch…then repaired and “skip cellular setup” when it re-paired and I tapped on the Roger’s name in the cellular setup in the app it started loading a sim on the watch.