Even if you manage to land features in Chromium without approval from Google employees, that will not help much. If Google doesn't want the feature they will disable it in Chrome, which is what matters for adoption.

As I mentioned in the article, Thorium is a Chromium-based browser that fully supports JPEG-XL. Here's the libjxl patch that can be ported to other Chromium-based browsers: https://github.com/Alex313031/thorium-libjxl