Yeah, there definitely is a library here. It is a small library: ~5 klocs. In part because it just does (a lot less) than React and leans more on working with the browser instead of a shadow dom, etc.

The downside is it does less than react. You will mostly have to keep the reactivity dependency tree in your head. Huge win for most b2b apps; A+ for internal admin pages; solid A for config pages in almost all apps; not a great fit for (parts of) highly reactive b2c apps.