Here's a tool that will let you convert .heic images to .jpg images on Pop!_OS or Ubuntu derivatives.
You'll need a few dependencies. Some you can get from apt repos:
sudo apt install libheif-examples
And the other from git:
git clone https://github.com/nitinkamra1992/heic2jpg
Now run the tool by changing into the directory and pointing the
heic2jpg.py script at your .heic images dir:
python heic2jpg.py -d ~/inputPlace -o ./outputPlace
Even better, don't produce .heic images on your Apple device. Change the default to .jpg.