Live photos are short videos up to 3 seconds. Are they longer? It may also happen, when the length can not be detected (0:00).

No, they're 3 seconds or shorter .movs.
When I got into the file details I can't see length anywhere, should I be able to? What would stop the length being detected?

We use exiftool for this as we can't directly read video metadata yet. So you need to enable json sidecar files, which slows down indexing a bit when indexing for the first time.

How do I enable json sidecar? I get a lot of .jpg sidecar files but not seen .json ones.

See our example docker-compose.yml files or run photoprism help.

Thank you, I'll give that a try, and what is the benefit of adding yaml sidecar files while I'm here?

They'll contain a metadata backup (title, description, favorite, private,...), so it can be recovered when your database gets lost.

Thank you!! That's solved it. Re-indexing a folder didn't seem to work after I made the changes, so I moved my settings/sidecar/cache folder and re-indexed the same folder and it's adding them as Live. Thanks again, I've really been enjoying curating lost memories in PhotoPrism, looking forward to seeing how it develops.