Hello,
Please connect the LVDS-HDMI card in LVDS0 connector as is in the next image:
JorgeCas_0-1733414696204.png
Then you need to use imx8qxp-mek.dtb device tree.
Set the U-Boot environment variable to imx8qxp-mek.dtb
=> setenv fdtfile imx8qxp-mek.dtb
=> saveenv
=> boot
Best regards.