[pootsbook]

I came across CSS Zero recently:

https://csszero.lazaronixon.com/lookbook/pages/overview

which bills itself as an "opinionated front-end starter kit" specifically for Rails and includes Stimulus.js code for JavaScript functionality.

It seems the benefits are that it is no build (pure CSS with CSS variables) and easy to modify and extend.

[psadauskas]

It also has the additional benefit of not being based on Tailwind, unlike most of the others listed in the original post and comments here.

[strzibny]

Yes, it's a good one. I'll include csszero in the updated version of the post.