Wi-Fi Calling does not work on my Moto G Stylus (2021).
I have a Prepaid AT&T SIM and a Prepaid AT&T Moto G Play. I have a Wi-Fi Calling option in Meny Phone/Menu/Settings/Calls.
When I move AT&T SIM card to Unlocked Moto G Stylus (2021) bought at BestBuy, I do not have Wi-Fi option.
But Wi-Fi Calling app is there available in the system, you can enable/disable. It just won't activate with AT&T Prepaid SIM in my case.
Could be available with other carriers.
See a screenshot attached from Moto G Stylus (2021) Unlocked purchased at at BestyBuy.