Is there a fast way to do that? I have a lot of them in “Photos” and I dread the idea of having to treat them one by one (export to another app, process them, import back in Photos).
Sure - I can keep all of them in iCloud and retrieve individual ones when I need them.
So it is more or less curiosity that’s driving me. A job for Automator?
If you can open them in Preview you should be able to save them as JPG
Using the Photo app, you can select the photos you want to convert, then export multiple ones as jpeg or other supported formats. If you wanted just those in a library, you could then reimport into a new library if you wanted those separate from the raw files.
Looks like there is no shortcut.