Raspberry Pi 4 HDMI Trouble [SOLVED]

The display seems to be similar to the one used in the thead “DIY streamer with volumio in standard 43cm box - #2 by lausiv”.

Maybe have a look at the settings in the “userconfig.txt” which has been posted over there and try out the values from that file in your “/boot/config.txt” (apart from “display_rotate=1”).