Similar to messages being posted at the request of other islands (Islay, Western Isles and Tiree) travellers to Mull are now seeing a pop-up message when buying a ticket on the CalMac website:
This has been arranged with the collaboration of Councillor Mary-Jean Devon, Mull Community Council and Marketing Mull & Iona. The embedded link currently directs to the Visit Mull & Iona front page, but this will be corrected shortly to go directly to the campervanning guide here.