I have setup certificate authentication using SCEPman (www.scepman.com) and InTune, SCEPman is a Azure Web App that can generate SCEP certificates but only if the device is registered into InTune. You can then either setup EAP-TLS on NPS or another RADIUS server, or use www.radius-as-a-service.com (same company as SCEPman) and point your Meraki SSID to them. With SCEPman there is a free trial, free version and a paid supported version. With radius-as-a-service you can get a trial, but it is something you need to pay for. If you do use your own NPS/Radius you need to use SCEPman user certificates as it does a lookup to local AD and cannot resolve Azure AD device ID. Hope this helps.
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