CopyTrans HEIC for Windows - A plugin that lets you view HEIC photos on Windows and convert them to JPG by right-clicking.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
iMazing HEIC Converter - iMazing HEIC converter is a free Mac and PC app which converts photos from HEIC to JPEG or PNG.
Heic File Converter - Free Software to Convert HEIC File to JPG / PNG / PDF
Aiseesoft HEIC Converter - Aiseesoft HEIC Converter is a useful tool that converts photos from HEIC to JPG/JPEG or PNG. You can open iPhone HEIF images on non-Apple devices conveniently.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.