Obviously niche, but the GOV.UK Design System is very well supported in Rails.

There's a form builder and library of components (built and maintained by me) which, between them, provide full coverage. Most new Rails services use them.

It's a good match because accessibility is one of the Design Systems' primary concerns so JavaScript is used very sparingly and only to enhance.

They're not official, only Nunjucks is supported by the Design System team.

https://design-system.service.gov.uk/

https://govuk-form-builder.netlify.app/

https://govuk-components.netlify.app/

Hey I've seen you work before I didn't realize it was an outside effort, also second the remark about accesssibility I wish my government could foster a project like that one.

We used your repo as inspiration for a separate US gov't design system (not uswds) at the beginning but ended up shifting focus to building web components just before I left.

Awesome work and hope your gov't sees the value of this work and oss work in general!