Step 1: Open the Settings app on your iPhone. Scroll down and tap on "Camera". Then, tap "Formats" from the list of Camera settings.
Step 2: Under Camera Capture, tap "Most Compatible".
That's it! Your iPhone will now shoot photos in the JPG format directly, while videos will be saved in the MOV format using H.264 encoding. You can change formats at any time by visiting the Settings app.
Switching from HEIC to JPG will not convert your existing library of photos on your iPhone. Only photos that you will shoot after the switchover will be affected. Same goes for videos.
There are two ways to convert your existing library:
1. Transfer the old files to a PC or Mac with the Automatic transfer setting enabled (iPhone Settings > Photos > Transfer to Mac or PC > Automatic).
2. Or, you can use third-party HEIC to JPG conversion tools downloaded via the Apple App Store.