In other words, HTM is a drop-in replacement for JSX that avoids the need for a compiler by using the corresponding language features. (At the cost of a few extra ${}s.)

lit-html and its ilk render directly to the DOM. They give similar developer ergonomics to React/JSX, but don't integrate with that ecosystem. They aren't a drop-in replacement for a JSX compiler within your React app; they're more of a competitor to the entire React paradigm.

Also of note is that, as a drop-in replacement, HTM is properties-first, like React/JSX. lit-html has you use different syntax for properties and for attributes.

Both are cool!