Hillzin Free for all topics - and the hub specifically has no onion domain because it isn't made as a service, it's made for logistics, support, feedback, and anything else our users need. But you free to start discussions about whatever you want as long as they follow our Terms of Use, and are tagged correctly.
For a general forum operated by The Onionz Project, take a look at the tor only DarknetBB. We also have two other clearnet forums for no particular reason.... namely talk@Onionz and app@Onionz, the later of which will likely be discontinued unless it's popularity unlikely increases.