i don't know where the myth started that offroad accidents aren't covered by insurance, but unless your policy has a statement excluding something it's covered. just read your policy, they follow standard language for the state (and pretty similar between states) so it's really easy to skim to the part where they list all of the exclusions. everyone needs to read their policy, you can usually get the full documents online.

you can't find out if your vehicle is covered offroad by googling, you need to read your actual policy. nothing you find on google will be helpful at all, the only thing that matters is what it says in your policy documents.

the closest I have ever had to anything that excludes offroad driving was a statement about speed exhibitions or something. i've used geico, nationwide, and farm bureau and so far no exclusions for offroading.