You can make a new folder where you will deposit the .heic images from your iPhone. You then create an Automator Folder Action assigned to this folder to automatically convert any image deposited into it as a .jpg.
Launch Automator from Applications folder. Choose Folder action and select the above folder that you created. Drag/Drop the following Library action to the right into the larger workflow window. Set your image type to .jpg.
Automator Library: Preview Action: Change Type of Image
When you deposit images into this folder from the iPhone, they will automatically be converted from .heic to .jpg.
For those that don't already know this, and it is undocumented, the command-line tool sips(1) can convert from .heic to other formats too.
sips -s format jpg magyar.heic --out magyar.jpg