Sorry, it's indeed a host issue, did not realize you are raising the question as a guest.
But when a search like a guest, i can go far beyond april 2020 to select dates !
(i am using the website, not the app).
But you have to realize when host have set their booking window to 12 months (which is rather common) , you will no see their listings, because dates more then 12 months after current date are not available for booking.