Discourse is a far superior open source forum software to phpBB, and it has a [url=https://meta.discourse.org/t/importing-from-phpbb3/30810]migration path from phpBB[url].

I've migrated my own forum from MyBB to Discourse, and never looked back. Would be happy to help.

I don't know if Discourse is the right way to go (I've seen it in action and found it rather confusing, but maybe I just wasn't used to it), but I also think the KDE forums are in a pitful and obsolete state and I would love to see a radical new approach like a completly new forum software instead of only small evolutional steps on a rotten basis.

I am not too fond of Discourse, but of course this does not mean it is bad. But I do think it is a bit of the new fad at the moment in forums software.
I think it depends if you like tags or not. I like the old hierarchical system much better, but that is me. I do not like Gmail either so...

I also think the current forum is beautiful and there is not much to change about it. Search works so anyone can find what they are looking for.

Also we do not need a new forum every other year.