Answer 1

Other popular css frameworks are Foundation and Materialize.
Instead of rely on built-in ui of css frameworks, I would rather use tailwind to build my own ui.
Visit https://tailwindcss.com/

Answer 2

Some say Materialize-css while other may say Bootstrap itself
You can best of both worlds with MDBootsrap 😊

Answer 3

I think this is flexbox and css-grids

Answer 4

I was helped you?

Answer 5

here is a bigger list
https://modernweb.com/8-bootstrap-alternatives/