Support is currently being worked on for Firefox, in the form of a rust decoder. Once that happens, there might be a little more pressure for adding support to chrome. I have also seen discussion about a Japanese company working on hardware support for jxl.

I would really like to see more support in open source software, especially libraries like opencv.

It is gaining momentum also outside the web where there is no dependency on Google, eg. in Gnome’s default background images <https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/commit/c34485585c90acd465ad7fc22a0f8d3c0aa976f3>

It will pick up. It will just take more time