I mostly use SolidJS. It's super lightweight - in many ways, it's just a wrapper around `document.createElement` and a signals library - so you've got a lot of flexibility to use it how you want. It works well for complex web applications, but the library part of it is small enough that you could probably use it for individual widgets on a page and not have too much overhead. The UX is React-like (hooks and JSX), but honestly feels simpler - JSX gets compiled directly to DOM nodes rather than a VDOM abstraction, and there's no "rules of hooks" to learn.

That said, it's kind of niche, which means you need to be more willing to write stuff yourself, so a good mainstream alternative is Vue. Vue is also signals-based and relatively lightweight, but still has a lot of batteries included and a wider ecosystem that is fairly strong. They're also great at taking the parts of other frameworks that work best and implementing them in Vue, but in a fairly considered way. I understand there's also some fairly battle-tested full-stack frameworks in the Vue ecosystem, although I've not had much personal experience of that.

Both libraries are signals-based, which is a completely different reactivity concept to React, which will take a bit of getting used to. But I suspect Vue will make that transition a bit easier - despite SolidJS's more superficial similarities to React, it behaves quite differently.