[kevmoo1]

FYI: Guetzli seems to have not been touched in ~5 years.

See https://github.com/google/guetzli/tree/master/guetzli

[Seirdy]

It evolved into Butteraugli which was incorporated into libjxl, which powers the reference JPEG-XL encoder. It also optionally powers libaom's encoding, which is in turn used by libavif and libwebp2 (for the WIP WebP2 image format).