"Dave, I think you know what the problem is, just as well as I do."
Clearly the author takes absolutely no responsibility for anything dangerous, illegal, destructive, immoral or just plain stupid that anyone does with these notes. Just a word of caution: 40kg robots are dangerous. 200kg petrol-powered robots with blades spinning at 200km/h are almost unstoppable. Think about a small person getting rammed at full speed with one of these. It will make The Walking Dead seem like a romantic chick flick. Think. Please.
Using ROS2. This is a big challenge just in itself.
Weed Detection. Mounting a face-down camera and analysing the image to detect weeds.
Weed Removal. Either through spraying or mechanical means (a length of wire like a lowering spring on a motor can dig out weeds without chemical environmental damage).
Pest Eviction. Chasing the kangaroos out of the yard (and maybe out of the paddocks, if kangaroos can be differentiated from sheep and alpacas ).
"I'm sorry Dave, I can't let you do that."