Node Sass should be replaced with more modern variant

[rustyrussell]

Node Sass does not yet support your current environment: Linux 64-bit with Unsupported runtime (127)
For more information on which environments are supported please see:
https://github.com/sass/node-sass/releases/tag/v7.0.3

ChatGPT suggests Migrate to Dart Sass...

I've downgraded to npm v16 for now...