I've never seen any rental boats beyond either houseboats, pontoons, or small runabouts - I think there's a place in lakefield that does small runabouts (14'ish footers I'd say, 4 passengers) stuff for example. There's a place on Scugog that does pontoons. Lots of options out there aside from those 2 I'm sure.
Actual non-houseboat liveaboards? I've never seen it. Skill requirements are too high and a "come along with you for the weekend/week skipper isn't viable on most boats unless the captain has separate living quarters where he/she can effectively disappear while the renters are enjoying the boat, and then there would be the additional costs of that (and finding a skipper who wants to do that), damage possibilities are too high to rent anything big without a skipper, and it's just not viable really from a lot of other perspectives including insurance.
Rental houseboats are built like tanks and can take a beating and keep going, and they DO take a beating. Which is why someone with zero experience can go rent a 30, 40, 50 footer and go full YOLO. I'm not sure how the heck these companies maintain insurance though, one smack into Lloyd and Veronica's Carver 56 and blamo, $20K in damage or whatever.
I have seen AirB&B boats, but they are 100% a "the boat stays tied up to the slip and doesn't move, you don't even have the keys" type things. If that's what you're looking for, then they are out there on AirB&B and FB Marketplace I've seen in the past.