IntercoolerJS / htmx looks like a really cool solution for server-side rendered HTML with client-side interactivity. All the hype is currently with https://hotwire.dev/ but htmx has more features, seems more solid and even supports older browsers like IE11.
The libraries cover a similar ground, but there are some fundamental differences. With Turbo, by default all your links/forms will use XHR to fetch new pages which do a full body swap (unless you want to use frames/streams or opt out entirely), whereas with htmx you have to be specific which links/forms and targets you want - there is an hx-boost attribute that does something similar but it lacks a corresponding data-turbo-permanent attribute (at least in the current production version) when you want to exempt certain elements. Both are valid approaches but it depends on what suits your requirements better.
In addition to the founder, there are at least 3 active contributors with significant contributions to HTMX. It may have started as a one man show, however, the knowledge is now spread over quite a few people who are exceptionally helpful.
