I have an aluminum ATV/utility trailer that only gets used a few times a year. I park it behind the garage, raise it off the ground and cover the tires. Of course, leaves and other debris get on the deck and make a bit of a mess.

Is there any merit to buying a canopy style roof, cutting the legs short and having the deck covered while leaving the sides open for airflow, or does the crap still blow under?

https://www.harborfreight.com/...tarpaulin-47676.html
and some bungees and rope

^^^^

The problem I've had with tarps is the tendency for snow to push them down and then the low spot starts to leak trapping moisture under the tarp until Spring. That's why I was thinking some type of pitched or curved roof support might be better.

I built a leanto off my shed to cover trailer. Tarps lead to animal cover.

I second the tarp problem leading to animal cover. I had two stray cats take up residency in my open fishing boat for a while.

I also have a utility trailer 6 x 10. I just treat the wood with Thompson's Water Seal and sweep/shovel whatever accumulates when I want to use it.

Sounds like a perfect excuse to build a new garage.

With aluminum, you really don't need to worry about corrosion of it sitting there in Minnesota. I would just jack the tongue up really high and block it that way so the roof has a very good angle so leaves fall off with the rain, or would be easy to hose off of the roof.