Helli Jia,
here are the good news...
I just received the mentioned display (Waveshare 4.3 inch HDMI LCD (B) 800x480) and did the following steps:
- Disconnect the DSI display
- Power the HDMI display via USB
- Connect HDMI port of display to Mini-HDMI port 0 of RasPi-4B board
- Connect Touch Mini-USB of display to an USB port of the RasPi-4B board
- Power RasPi-4B - the display is detected automatically.
- Build "HelloWorld" application according Getting Started documentation
And: it works...
At the beginning, the display is a short moment black (I assume when the display mode changes), but then the GUI application appears as expected.
Can you try it once more?
Are you using the latest Raspberry Pi OS Lite (Bullseye)?
EDIT: Make sure to connect the touch!
Best regards,
Manfred.