Yeah note that Google only said they're now open to the possibility, as long as it is written in Rust (rightly so).

The patch at the end of that thread uses a C++ implementation so it is a dead end.

Rick specifically said commitment for long term maintenance and meeting usual standards for shipping. The implementation was abandoned in favor of a new one using rust, so not necessarily a dead end.

I meant the C++ patch is a dead end; not JPEG XL support in general. Seems like there's a Rust library that will have to be used instead.