My experience has been the charter companies provide a cable and lock - definitely the type that could be cut with heavy shears, no need for bolt cutters, but at least, as has been said, petty thieves will move on to easier targets…I’ve never given locking the dinghy a thought, but probably will this year while down there….
Related: what d’you think about locking the big boat while ashore or overnight? Also never given a thought in the past, in fact, I’m sure I’ve slept or left with all doors and hatches open in the past- is this becoming a not recommended practice?