Not really self-hosted in the typical sense, but Obsidian with the Tasks and/or Kanban plugin synced through a (self-hosted) solution of your choice could work?

Haven’t tried the whiteboard tool in Google keep (didn’t even know there was one), but the Excalidraw plugin for Obsidian should cover almost any whiteboard use case I can think of. A bit more limited but also good is the native Canvas plugin in Obsidian.