This bug is still present in UE 4.23:
UE-66032
To test, open a new project with a large landscape. Set the max draw distance to something like 100000. Change editor view to game mode to confirm landscape farther away disappears. Try to change the max draw distance back to zero or actually any other number, but the landscape continues to disappear at the first distance set.
If there’s workaround, please let me know, as I’d prefer not to redo the work on the landscape again.