The free Smart Tag seems to work well with the S21, except for one documented feature: the tag is supposed to ring the phone when you press the tag button twice, but it doesn't do that for me. Instead, the tag gives two brief beeps (the 2nd higher pitched than the 1st). The phone has Offline Finding enabled, and it does show up on the SmartThings Find map. The phone can ring the tag properly, but not vice versa. Is there some other setting that's needed for the tag to ring the phone?