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Unfortunately it can not be accessed from inside.  You would have to pull the AC out to do that.  I would try to come up with some type of screen that you can fasten over the exterior of the vent so you can remove it when you run the AC so as to not restrict the airflow.  Check out Sea Biscuit Metal Designs.  They just came out with a metal cover for the vent that attaches and the vinyl cover then goes over it.  It is meant to restrict water intrusion when towing the trailer but can be left on during storage and during use.  Though it may restrict airflow a bit.  Maybe you could attach some screening on the backside of it to keep the bugs out?  It fastens on and is supposed to be very easy to remove if.  I'm considering getting one. 

https://seabiscuitmetaldesigns.com/product/tab-400-a-c-vent-cover/ 

And here are some pics of the backside of the AC.   I removed ours this spring to just have a looksee at the Alde convectors and to see what was back there.  As you can see the back of the exterior vent is not accessible.  The last photo is the Alde Glycol loop behind the White panel you see in the first photo.  

My son and I replaced the axle on our 2019 t@b 400 bdl in about 90-mins (faster had I helped but I didn't want to ).  Gear was a Harbor Freight Trolley Jack, two jack stands, Dewalt 1/2" drill with sockets and Dewalt Impact Wrench.  What took the longest was removing the rear and side screws holding the under carriage skirt on.  We didn't remove it completely, just the back and screws down each side to just in front of the tires.  Once on jack stands, we used the trolley jack to hold the axle while we removed the bolts then reversed the process.  Seriously, 90-mins and most of that was walking back and forth to the shed for tools.  Of course we had a few beers, did some joking, and got distracted a few times. 

I wanted the camera mounted higher than the license plate.  I use the camera asa rear view camera as well as a backup camera.