I started using the cymru bogon servers and have a routing filter that takes the bogon community 65332:888 and sets the type as blackhole. Routes for bogons look as expected on IPv4 with type=blackhole but on ipv6 routes it shows type=unknown. Is this a bug or is there a different configuration for IPv6?

I believe the reason for this is the old Linux kernel in RouterOS which does not support blackhole routes in IPv6. You might consider using unreachable routes as a workaround if this is an issue for you.

OK, thanks for the information. I will use unreachable instead.