Pinafore is an alternate web client for Mastodon. Here are its high level features:
Pinafore stores data locally in IndexedDB so it even works offline.
On GitHub: GitHub - nolanlawson/pinafore: Alternative web client for Mastodon
It’s not currently setup to be full static — CSP headers and SOME dynamic routes.
I think this would be a very interesting example of a user customizable front end app, that would appeal to the existing Mastodon community.