Tried 2 different short patch cables. Same results.
Then tried with the brand new, never been used cable that was just sent to me with new Cisco VoIP cable. That one negotiated to 1Gbps. Finally. I'll keep watching the darn thing and see what happens.
Wish there was some way to get diagnostics on the negotiation from either of the devices, Zyxel modem or Meraki appliance.