Jon Sneyers, one of the developers of FLIF, since combined it with ideas from various lossy compression formats to create a successor called the Free Universal Image Format (FUIF), which itself was combined with Google’s PIK format to create JPEG XL. As a consequence, FLIF is no longer being developed.[1]

The format was initially announced publicly in September 2015,[6] with the first alpha release occurring about a month later, in October 2015.[2] The first stable version of FLIF was released in September 2016.[7]

So, not new and seemingly no longer developed separately from JXL.

https://en.wikipedia.org/wiki/QOI_(image_format) seems interesting, though.