How to join purism matrix room with element?

I’ve got the Element app for linux, and I’m signed in. I go to “Explore rooms” and paste (found here) in the search bar, and hit the “Join” button that shows up.
I’m greeted by:

Many months ago, the Purism rooms had some issues with trolls setting up spambots, so most of the Purism rooms had to be made invite-only. I am not part of the heads room, so I cannot invite you, but I’m sure there are some other folks on the forum who are.

Maybe even @MrChromebox or @Kyle_Rankin can help you out.

That room is invite only due to some issues we had with spammers.

send me your matrix handle via private message and I can invite you to that room

I would like to join to the HEADS room for Pureboot related questions. I cannot dm you? Don’t know why…

Thank You

(By forum configuration) new users are not permitted to send PMs. @joao.azevedo can work around that.