Does anyone know how to meet/unlock Boulder?
Meet all sorts of adventurers and co-workers here in Flaming Flagon 路 By
Late reply but the game's page features characters mostly to look forward to as the game continues to update as you can see with most of the sketched designs. We'll see them pop up eventually but it will likely take some time.
As for Boulder, they'll be in the next Patreon update so for public builds, we'll get to meet him next-next update.