Hey there @SHobley06, welcome to the EE Community!
I've had a look around with this one, and it doesn't look like Samsung have updated their watch compatibility guide to cover the Watch7 series just yet.
This does go as far as the Galaxy Watch6 though, and at that point the requirement was Android 10.0 and at least 2.0 GB of RAM on the connected handset.
The S21 has gone up to at least Android 14 with it's software, so my hunch here would be that this should be all good to go.
If you did encounter any compatibility issues though, you have 14 days to change your mind if you purchase online or over the phone 😊
Peter
