I believe that the developer of FLIF integrated much of the tech into JPEG XL. It seems to happen a lot with codecs (e.g., Xiph's Dalaa tech merging into AV1,

I believe that the developer of FLIF integrated much of the tech into JPEG XL. It seems to happen a lot with codecs (e.g., Xiph's Dalaa tech merging into AV1, or Xiph's CELT and Microsoft's SILK merging into Opus). I see FLIF as the prototype and JPEG XL as the production version.