I have never participated in free cloud mining, but I have previously invested in the eobot cloud mining platform and it really just disappointed me. If at that time I used the money I had invested in the eobot to buy bitcoin or ETH, I would probably have become a wealthy person now.
So I strongly recommend not taking part in cloud mining, even though it is free. In case you can invest in a reputable mining platform, it is also very difficult to profit for you.