Guy Glantser notes an issue with Availability Group documentation:
In SQL Server 2017 Microsoft added a new flavor called Read-Scale Availability Groups. This is different, because the goal here is not high availability or disaster recovery, but rather read-scalability. As opposed to the other flavors, in RSAG there is no cluster, and there is also no automatic failover mechanism. But you can set up multiple secondary replicas with read-only access and load balancing, and offload read workloads from the primary replica. This is a great scalability feature, and you can read more about it here.
Now, if you check Microsoft documentation regarding the editions and supported features of SQL Server, you will be happy to see that RSAG is supported in Standard Edition. I was happy to see it too. Unfortunately, if you try to set up a Read-Scale Availability Group on Standard Edition, it will not work. You will only be able to create a Basic Availability Group, as discussed earlier.
Click through for the answer, as well as what you can do in Standard Edition.