I use AlpineJS for reactivity. Along with JS Template literals[1], I can reach quite close to the ergonomics of having react like re-usable functional components without bringing in the whole complexity of react ecosystem. Works quite well for smallish projects.

For styling I pick up Bulma CSS if I need some more complex components (tabs, modals etc.) or TailWind if I just want to pepper a little styling here and there. All this loaded directly from CDN. No build step, no server etc required. You easily do debugging from browser console.

I have made a few internal tools like this which my co workers use everyday.

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...