Thanks! It does not use a css/ui framework. It is something I designed and build from scratch.

I believe they didn't use any CSS framework, it's handrolled Sass styles (other than Normalize and Font Awesome).

https://gitlab.com/bramw/baserow/-/tree/develop/web-frontend...

They do use Nuxt, a fullstack framework for Vue.js, which is style-agnostic.

https://nuxtjs.org/