If you are part of a hacker space you could always get tickets through that quite easily. I think it’s great that they are supporting their original core audience like that.
Those hacker spaces only get a limited contingent too, and the hacker space will expect you to help set up their assembly if you get the ticket through them.
I can't help but read your "will expect you to help" part as trying to say something negative. But if they helped you get a ticket, helping them for an hour or two to setup their space feels like the least you could do.
Yes, limited contingent, but that's also expected with a limited number of seats at the congress. I'm part of two hacker spaces and none of them expected any help with setting up their assembly.
Have you checked if they have an open day? Many have a dedicated public day every week where you can just drop by and if you are interested someone will probably happily assist you with becoming a member.
Otherwise joining their IRC and asking there could also be an option.