Apple chose storage. Recipients chose JPEG.
iPhone, iPad, and Apple Photos write HEIC because it packs a lot of detail into a smaller file. That is a good default on a 128 GB phone. It is a bad default the moment the file leaves iMessage. Windows may show a blank thumbnail. WhatsApp-to-Android threads ask people to “download to view.” HR sites list JPG only. Changing Settings → Camera → Formats to Most Compatible only helps pictures you take after that toggle. Your last three years of travel still sit as .heic. This spoke is that library problem: take a still from Photos or Files, run it through Edge (eligible singles free), and send JPEG. You can keep High Efficiency on for new shots and convert only what you share. Live Photos are a still plus a short movie; export the still first. For Safari-on-the-phone steps, the mobile spoke is more specific. For AirDrop-to-PC codec drama, use the Windows & Mac spoke.
Keep High Efficiency, convert on demand
You do not have to give up Apple’s compact files on disk. Convert the ones that must travel. Keep masters in Photos or iCloud.
When the phone is the only computer
Safari can run this page. Prefer one file on cellular. Giant rolls belong on desktop Pro VPS, not an LTE tab.