Always On Primary Replica On Prem, Secondary Replica On Azure
We only want to have 2 replicas, one on-prem and one on azure. Is this possible?


Yes, it's possible. There are extra items you'll want to think about such as having a domain controller (if ad-attached clustering/cluster at all is used) and what type of pipe you'll need, region and latency, load balancer setup, etc., but it's not a hard requirements to have more than two replicas. Most have two replicas locally for HA and the Azure one for DR.


  have read the documentation to use the "Add Azure Replica Wizard" [...]


That wizard no longer works as it was based on the classic Azure model and is no longer available or viable. Disregard using the wizard. You'll want to deploy this via a written script or by hand (Azure web gui) after all of the required infrastructure pieces are decided upon and understood. Obviously setting up a test environment to see how things behave would behoove you.