Payment makes it a business pursuit
Lending an RV to a friend is personal. Renting it to somebody for money through a platform is commercial, and personal policies exclude business pursuits. The umbrella follows the exclusion, so the activity most likely to produce a claim is the one sitting outside the cover.
Platform protection is not your insurance
Sharing platforms provide their own cover with their own conditions, limits and exclusions, and it operates on their terms rather than yours. Treating it as equivalent to your own policy is how owners end up relying on something they have never read.
Your own policy may be jeopardized
Where a carrier learns that a vehicle is being rented out commercially, the consequence can extend beyond declining one claim to non-renewing the policy. Disclosing the activity and arranging the right cover is considerably cheaper than that outcome.