Hi Claude.
Not all of the crowdfunding sites are real transparent when it comes to results on specific deals. In many cases, it's because the deals are being offered by 3rd party sponsors so it's a matter of whether those sponsors want to show their performance publicly or not.
One site that does a great job of showing returns on realized investments is RealtyMogul. You can actually browse all of their completed deals and see what the target returns were vs actual returns.
The last time I ran the numbers on their historical deals the average IRR was 17.2%. We'll be updating that data soon and will report here once we do