It's very, very much active. It's used heavily at Google in apps, Chrome, YouTube, Waymo, etc., and by companies like Microsoft, GitHub, Netflix, IBM, Adobe, Maersk, SAP, Apple...
One big difference to the projects you listed is that lit-html doesn't require a compiler. It's plain JS, and is fast because it uses template literals and built-in HTML parsing/cloning to associate expressions with DOM.