First

[Seweli]

Not sure PHPBB forum is the bestr ergonomy, but well... it's public and it's not Reddit

[pandunia-guru]

PhpBB is what my web hotel had, so I installed it. It is an old one but it has stood the test of time and it is still updated. There are no modern features like social media interaction, threading, upvoting and downvoting, but sometimes simpler is better and we can live without them.

I can change the "skin" of this forum and make it more personal looking. There are readymade alternatives at https://www.phpbb.com/customise/db/styles-2 and it's possible to customize them.

[seweli]

No upvoting is clearly a killer feature. No more bloating stuff.

It's public and indexable by search engine.

And everyone still know phpBB forum.

It seems to be a very good idea for an auxlang that need visibility.