Hi guys,
Do you know if exist something like ebay, but based on crypto?
You may need to be more explicit. Do you have an idea you wish to put up and just trying to survey if such idea has already been implemented? If this is the case, if you come out plainly, two things will happen. You will get better recommendation And or you will get partners who may be willing to work with you. What exactly do you want or has that been answered already?