Start a group., Find a way to communicate with them (fix Slack client?) After initial enthusiasm, you’ll need something to keep it ticking over. You’ll need a Wiki or similar for new people…
If you’re not going to lead it, you’ll need to find a leader.
Think about scope. To me, the community looks a bit scattered and probably feels unsupported. The group could work in a semi-official capacity doing the neglected private user side of Jolla’s business.
We could do with something like developer liaison. Clarifying developer needs, feeding back from Jolla, keeping track of their ‘holidays’.
Then, when you know what you want to do, ask Jolla to appoint a liaison.