Make CSS compatible with Chromium 87 (no :where(), no oklch, ...) and an external CSS lib

[DJ-caddev]

Hello,

I'm using a Qt5.15 browser, running Chromium v87.
I cannot upgrade Qt for various reasons.

My frontend is running a Vue3 bundled with Vite. I'm am using TailwindCSS + DaisyUI libraries for the style part.
I stayed in Daisyui V3 because V4 uses oklch notation for colors, which are not supported at all in Chrome v87.
I have now a new issue... The :where() selector is not compatible either (https://caniuse.com/mdn-css_selectors_where) with the Chrome v87.

I did find build.cssTarget settings, but it does not seem to parse libs at all.

export default defineConfig({
   //...
  build: {
    cssTarget: ['chrome87', 'edge87', 'firefox77'],
  },
});

Other note: I'm using PostCSS with tailwind, which uses autoprefixer that uses browserlist under the hood.
I have added in package.json:

{
  "browserslist": [
    "Chrome 87, Edge 87"
  ],
}

which seems to be right too.

Please tell me how you would achieve CSS parsing/polyfill to have :where() selectors from DaiysUI classes replaced by a compatible CSS instead (and other properties too, how to replace oklch for example, in DaisyUI?).