Hikey960 ubuntu system connects HDMI no image output

After flash ubuntu on Hikey960, I used HDMI to connect the monitor, which was black with no image output

Does the display work with the first party software? Hikey960 has some limitations in the clock generation hardware that menas some display devices will not work. However, to be honest, I’ve no idea what the ubuntu image does even with a working display.

Thank you for your reply! The first part of Ubuntu also has no HDMI output, but the same display Android and Debian can display normally.