AngWay
users can use any eSIMs installed previously on the device.
-https://grapheneos.org/usage#esim-support
Further anecdotal confirmation
#29540
Esims stay even after a factory reset. (On GOS at least)
"Duress pin" feature will wipe your phone deletes esims.
You can go back and forth between GOS <-> stock OS and keep your esim
An aside, One user enabled a duress pin then later wanted to change their duress pin. The phone asked to authenticate themselves to change this.
They typed in their duress pin to authenticate themselves. This wiped their phone. Only type the duress pin to wipe the phone.