I think the best security we added to trailer was motion lights. I replaced the light above door with a motion light that is wired to 12v (also great for coming home when it’s dark) and added 2 motion solar lights outside rv on side and back of trailer above our bikes we keep on bike rack.
https://www.amazon.com/dp/B077XQZ3RZ..._ftPdCbY7AWK87
We use a netamo welcome security camera in the fifth wheel (needs internet connection which we do through a hotspot always in trailer) that will alert us if there is any motion or if a alarm goes off (smoke/fire, carbon, propane detectors). There is no monthly fee and can get alerts through app on phone and upload to Dropbox.
We have a dashcam in truck out front and back window that records on motion so I park the truck pointed at trailer.
We also have a German shepherd but she is often with us.