Raspberry Pi 3 b+ and waveshare 7.9" screen on LibreElec 9.2.8

Hello everyone,

I have Raspberry Pi 3 b+ and waveshare 7.9" screen attached to it.

I added following to config.txt file to run raspberry pi with this screen and it is working while in boot:

max_usb_current=1
hdmi_group=2
hdmi_mode=87
hdmi_timings=400 0 100 10 140 1280 10 20 20 2 0 0 0 60 0 43000000 3
display_rotate=3

but when gui starts the picture does not fit on the screen and under display settings it seems like the selected option is 0x0p

when I try to change it to native resolution (which is 400x1280) screen is stopping to work.

does anyone know what to do please?

Regards,

noone can help about that?