i'm approaching this issue from the other end: using a subset of html (and careful progressive enhancement) to build a site which works in every browser since the earliest days of the web.

i am pretty confident that, although i haven't tested it, it would work in both kosmonaut (if you download and save the files and submit content with something like curl, but use kosmonaut to display it)

i bet it would also work with that apple se / raspberry pi combo also in today's top page.