The problem with knock-off is they don't have the Hero bus on the back of the camera. The Solo gimbal is designed to plug into this connector and it allows Solo to control the camera. People have crammed other camera into the gimbal but the Hero bus connector sticks out and makes it a tough fit. They do work with the live video as long as the camera has hdmi out and the right connector.
I tried the Xiaomi Yi camera with my Solo and could NOT get live feed. I tried playing with camera settings, swapped the hdmi cable with the 3DRelish ribbon cable and nothing. Installed a Gopro 4 Black and voila, live feed first try! Others have had luck with the Yi and live feed but for some reason nothing worked for me with that camera. I was even starting to think my Solo main board was messed up.
I tried an xiaomi yi with the Solo gimbal, I had to buy a HDMI extention cable and the fpv worked but this setup was very cluggy and not well balanced. I then got an Eken 7 HD camera, about $60.00, it has the HDMI position the same as the GoPro and can be strapped in with velcro and balanced ok and give fpv, but the 1080/30fps is only so so, it doesn't handle fast movement well.
So I finally spent the money to buy a GoPro, $300.00 for a new GoPro 4 Black with an included attachable touch screen from B&H, now I get good, fast action video with complete camera control. If you want good action video on a Solo gimbal, GoPro is the only choice unfortunately. GoPros can be found for less used, but I bought 2 GoPros used , both defective, so be careful.