CopyTrans HEIC for Windows - A plugin that lets you view HEIC photos on Windows and convert them to JPG by right-clicking.
Fragment - A powerful image viewing suite with advanced metadata info
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
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.
ImageGlass - You can use Image to view your digital images and photos of many different formats.