The main two contenders were .avif and .webp. For a few reasons, I selected .avif and in hindsight I think it was the better, choice. Both would be objectively better than jpg or png.
With JPEG XL ... hmmm. AVIF is not perfect, in particular when the compression rate is very high I noticed that some photos lose a lot of intrinsic quality that is not instantly obvious; I noticed this when I took various pictures over the years from outdoors. Still, AVIF beats jpg and png just about on every metric when compression is required. With JPEG XL I guess I have to re-evaluate, but right now I am still sticking to avif. The two factors that will be important for me is compression ratio and quality. I am ok with a bit of loss of quality, if the compression is better, but I am not sure JPEG XL beats AVIF here clearly either, so I am not sure what to do with JPEG XL.