On Apple's iOS, you can not change settings directly inside the camera and then choose the preferred format for each shot.
The change is really at the system level.
Go to Settings and select Camera.
In the Formats section, you can then choose the "most compatible" mode, that is JPG.
Once activated, all photos will be acquired again with this standard and therefore compatible with all software or editing services.
It was easy? Did you think it was possible to take pictures in JPG instead of HEIF?