What version are you running?
Wireless bridges running version 27.X or below only support a single VLAN. If support for multiple subnets is a requirement for the deployment, a layer 3-capable device will be required. MR repeaters will only send/receive untagged traffic on its wired interface regardless of the configuration of the SSID in use.
Starting 28.1, Multi-vlan support was added.
By extension, wired clients across the mesh link do not support the use of VLANs applied by Group Policies.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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