I would recommend Bitblender which is in my signature. They are TOR based which means you get the most privacy, and they're one of the most long running mixers out there after bitmixer closed down.

Second choice would be chipmixer. They provide a very good service with an active customer support, the only downside is that chips sometimes run out and they launched this year making them pretty new.

Just don't go out and use random ones, otherwise you'll get scammed.