Open the Settings app
Tap Camera
Tap Formats
Select Most Compatible
New photos will be saved as JPG instead of HEIC
To convert existing HEIC photos, open the Photos app
Select the HEIC photo
Tap Share
Tap Save to Files or send it through an app that converts it to JPG
Use a shortcut or third-party app if you need batch conversion
On a Mac or PC, transfer the photos and export them as JPG if needed