Mastro looks like what I do for my offline-first, rendered from Service Workers. I just compose html template string literals and stream them back to the front end. The lib I use for HTML is a bit more powerful though. It is a very elegant way to program.

https://github.com/jon49/Soccer

Thanks, this one? https://github.com/jon49/html-template-tag-async Looks very similar indeed! What makes it "more powerful" than Mastro's html template?