External monitor is flickering when connected to iPad Pro 2020 through HDMI

How do I solve flickering tv problem when it connected to iPad Pro 2020 through HDMI? I already made sure that the frame rate setting on both devices are the same: 60Hz. I used third-party adapter and it works fine on other Type-C device: Samsung Galaxy Note 9. I also used proper HDMI cable. Or is it just a matter of have to have Apple adapter not other brands?