Can we write FLIF off, or does it still have a chance at wider adoption? I remember quite a positive reaction on release, but don't see it in the wild, unfortunately.

https://flif.info/

There was also an update to it called FUIF - Free Universal Image Format

https://github.com/cloudinary/fuif

But it too got superseded by JPEG XL (.jxl) https://jpegxl.info/