Good [insert whatever your local time of day is]!

Does anyone have any experience to share with the Barn Owl boxes sold by, e.g., barnowlbox[.]com (or similar sites)? Are they safe for the owls and sturdy? Would the pole-mount option actually be suitable? To someone like me at first glance they seem decent enough, but I don’t know what I don’t know.

Alternatively, if I was going to build one myself, what would be a safe, long-lasting material? I assume treated lumber is out of the question since it’s chemically adulterated, but what about composite “lumber”, cedar, or something else? This probably wouldn’t be my first choice since I’m not super good at building things.

Thanks in advance for any insight!