Like you, I'd like to find a trunk-mount bike rack for the Model Y, but after looking closely at the Y's back hatch, I don't think we'll be able to find one - here's why: If you look closely at the front lip of the hatch, you'll see that the glass portrudes beyond any metal:
View attachment 641037
What this means is that the clips for the rack will be transferring the weight of the bike(s) into a shearing force acting on the glass (trying to pull it off the back of the car). I'd be
extremely concerned that hitting a bump with a heavier bike on it (> 25 lbs or so) could either crack/shatter the glass or possibly cause it to detach over time.
I have an
Allen Sports Ultra Compact single bike rack that I used hundreds of times over about 8 years on my Nissan LEAF with a 20 lb road bike with great results. I think it will work as well on our Model 3 (again, only with a light bike, due to the aluminum trunk lid):
View attachment 641046
But I don't think I'd trust it on the Model Y except in an emergency, and then only with a light bike. 60+ lb. electric bike? No way.