I think for apprentices, honestly it depends on the spomdor/mentor, and the State and dedication and time of both the apprentice and Mentor.
Its cos owls hunt at night, and people are up during the day, so people mostly just use owls as educational birds.
I would be willing to take on that challenge if I had my darn falconers apprentice licenseeeeeeeeee
It would be illegal and frowned upon by the falconry community as a whole for an apprentice to take an owl chick. Plenty of falconers who take GHO's hunt them during they day, as they are crepuscular, instead of strictly nocturnal. There are alot of factors as to why very few are successful at hunting with them. If you haven't you should totally get in contact with some local falconers. I know of one in Vail and a couple in Tucson if you're having trouble through the state club.