(It won't let me edit my answer (probably because the moderators still haven't approved my posts after 11 hours), so here are my findings after some more testing)
Forcing DirectX 11 via -force-d3d11: Works.
Forcing OpenGL via -force-glcore: Works.
Relying on the game to pick the correct option: Fails, even with the latest drivers.
I have other games that need D3D9 (which is what the log says the game is trying to use), so I definitely have it installed. Other Unity games work fine.
