Is there a good place for the jammers to hang and work/chat about the jam? The official arch discord seems to be focused on keeping rooms channeled to sync/async runs, no general.

On the official Archipelago Discord there are Programmer's Lounge and Programmer's Den voice channels you can use (they are often vacant). Also you can use Start Game voice channel to start a new VC and rename it to be more fitting for jam discussion.

I asked AP Discord mods about it, either one is good.