I was going over the README here: GitHub - realm/realm-cpp: Realm C++
It says:
Realm is a mobile database that runs directly inside phones, tablets or wearables. This repository holds the source code for the C++ SDK Preview.
While at the same time, I see that it is already post version 1 and also this PR: Remove experimental namespace, Remove Alpha SDK by leemaguire · Pull Request #131 · realm/realm-cpp · GitHub
Makes me think if that “Preview” was just left out and needs to be removed.