Theoretically, a device certificate is valid only for the machine added to the domain.
Certificate authentication: This is used to configure the trusted CA file that is used to authenticate client devices. This configuration is only required if you need to authenticate client devices with a certificate. Only certificates PEM format are supported at this time.
I'm not sure if this would work as the options you have with Meraki VPN are limited.
Perhaps you would have more options if you were using Cisco ISE as a Radius server.
I suggest you to open a support case.
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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