Wubbo
Chieftain
Apparently it's very easy to reproduce this bug: just make a beeline for Political Philosophy without learning Military Tradition or Mysticism first. If you change government types, you will not have any available Wildcard policies and the game will prevent you from proceeding. You also won't be able to change government types back to Chiefdom, because you already committed to a government change that same turn.
Civics tree showing the path to Political Philosophy, with no Wildcard policies along the way:
Policies screen showing no Wildcard policies available, with the "Assign all Policies" button disabled because not all slots are filled:
Seriously dumb. Hopefully this will be fixed soon. Fortunately in the early game, not very much happens each turn so I can reload the autosave easily.
Civics tree showing the path to Political Philosophy, with no Wildcard policies along the way:

Policies screen showing no Wildcard policies available, with the "Assign all Policies" button disabled because not all slots are filled:

Seriously dumb. Hopefully this will be fixed soon. Fortunately in the early game, not very much happens each turn so I can reload the autosave easily.