Thanks, I’m able to reproduce the problem now. It has nothing to do with the specific photo, but the fact that you’re uploading from the Photos app (camera roll) in Safari. The Photos app converts the HEIC to a JPEG behind the scenes, before uploading it to Micro.blog. It gives the new file the file extension .jpeg so you’re affected by this bug.
When that bug is resolved, you should be able to upload from the Photos app in Safari just fine. Workarounds until then:
- Use the iOS app
- Upload HEIC photos from the file browser instead (not the camera roll)