I think Netsurf requires a 16 bit resolution?
That's what I heard as well but there will be a solution to this with the Indivision AGA Mrk2 (high/true color chunky modes!) which should be released in the next couple of weeks.....sorry months.
I would have a look at doing an AGA version of this myself but I've got such limited time for 68k coding so I think my efforts are better spent elsewhere.