You are not going to be able to integrate with EntraID without spending some more money.
Splash Access have a solution for onboarding both wired and WiFi devices. It is 100% cloud-based. You could have a chat to them.
https://www.splashaccess.com/
If you could reduce the scope to WiFi only, and you have Intune managed devices, you could buy a subscription to Cloud PKI. Meraki MR can authenticate devices with an issued certificate then.
https://learn.microsoft.com/en-us/mem/intune/protect/microsoft-cloud-pki-overview
If you are using EntraID (by that I assume you are cloud-native and don't have Active Directory) - have you considered going 100% zero trust, and migrating any app that does not have zero trust to being zero tust capable? With this approach you no longer care about local network security.
Actually, the more I think about it, the more I think you should look at SASE. The service you would want with your Meraki system is called "Cisco+ Secure Connect". I think you need to look at this as you need a far more holistic approach to be able to tick your boxes off without a traditional NAC system.
https://documentation.meraki.com/CiscoPlusSecureConnec