'Allow Client Side Navigation' no longer appears to register Client-side navigation in 4.20. In 4.19 the logic that was setup to check for it returns both Client and Sever Side navigation systems as True when they are initialized. In the attached 4.20 project only Server Side Navigation properly initializes.
Results: Navigation is not created clientside
Expected: Navigation is created clientside
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-60438 in the post.