I have successfully activated syncthing on a NAS and on 2 phones.
I’ve created a read-only share on the NAS and what’s needed on the 2 phones for the content to be duplicated on them.
The NAS knows the 2 phones, and each phone knows the NAS.
If I enable mutual phone recognition, and one phone is up to date
while the other isn’t, will the phone that isn’t up to date sync from the other phone if the NAS is switched off?
“Receive only” just means that any local modifications are not propagated to other devices. Relaying changes that originated on another device is not affected by that.