Is there any way to transfer the Fruit UT from one friendly ship to another?
Nothing comes to mind. It can be destroyed by effects that target cargo or treasure, and it can be converted into a cannon with Carbon Charlie’s ability, but otherwise you’re mostly stuck with it.
Is it legal to explore a flotilla to give it the Maps of Hades UT? (so the UT can be “hidden” away and basically made irrelevant)
Flotillas can be explored by other ships. You’d still have to roll for the Maps’ effect before the Flotilla could take an action, and even though it technically can’t move, the block on giving it other actions would still apply.
Also, it would be hilarious to see the other ship get repeatedly moved away while trying to dump that UT on the flotilla. 😛