Recently, I discovered RFC 6570 and think it's a great basis for a URI router, especially given its designed for creating links too, which is useful in the context of building htmx (and other hypermedia) apps.
With SPAs we've put a decent amount of thought into the tradeoffs between URI length, and putting enough context in each link to reconstitute the app state from a combination of local-storage, data requested from the server, and pure frontend db state (navigation location, parameters, etc...)
Perhaps there's some connection here as well with datafy/nav, there are increasingly spaces where REST-ish graphs of data are arising and capitalizing on the formalism in reference/navigation with something like this seems like a good idea too.