From the folks at Basecamp comes Turbo:
Turbo accelerates links and form submissions without requiring you to change your server-side generated HTML. It lets you carve up a page into independent frames, which can be lazy-loaded and operate as independent components. And finally, helps you make partial page updates using just HTML and a set of CRUD-like container tags. These three techniques reduce the amount of custom JavaScript that many web applications need to write by an order of magnitude.
Nice, but that “without requiring you to change your server-side generated HTML” part is not exactly true though, as you have to sprinkle some turbo-* custom elements and data-turbo-* attributes all over your markup. Once those are in place Turbo will do its thing and progressively enhance the experience.
If you want to do more than the features provided by Turbo you can bundle it up with Stimulus and Strada. All three together are published under the name Hotwire.