From the views of ISO, JPEG Committees, no, they are not patent encumbered.

From the view of AOM members or supporters, yes they are or at least not clear.

Do you have any sources on that? And who would be the one making any claims relevant to JPEG XL or asking for royalties?

Because I have not seen anyone other than Cloudinary and Google declare to have patents relevant to JPEG XL, and those two parties have explicitly granted royalty-free licenses. So to me the situation is as clear as it gets.

Of course it can always happen with anything less than 20 years old that a patent troll appears and makes claims. This has not happened yet though in the case of JPEG XL.

>From the view of AOM members or supporters, yes they are or at least not clear.

Sounds complicated. Why not PNG? :-)

PNG is really bad for anything photographic. As in, it's pixel-perfect, and the images are also absolutely enormous, unusably so.

PNG, while being a very nice format, is dramatically larger than JPEG, JPEG-XL, AVIF, HEIF etc. For multi-megapixel images that size cost adds up.