@SPO_SCIBFthis was a long way to go, but I'll tell you 🙂
The short answer is: I've opened a support ticket and asked when network objects will come into public beta.
The full answer is: After Meraki praised the new feature at a roadshow event in November in 2019 (!) to be released soon, we've opened a support ticket in January 2020 asking when the feature will be GA. They answered that it was still in closed beta and that we have to reach out to a special mail address to get into this. I did that and never got a reply.
2 weeks ago, the issue came back on our agenda and we once again opened a support ticket asking when it will be GA. They again answered, that it is still in closed beta. Afterwards, I've got contacted by our sales rep who organized to get us into the beta. Weird thing about it is, that in the onboarding webex they told me that it will be public beta in 2 weeks. If the support just had told me that, I would have just waited the 2 more weeks...
So to conclude, I would suggest you to just wait the 2 more weeks until it'll be public beta.
If that is not going to happen, I would suggest to contact your sales rep!