Can't boot rock pi x from sd

Hi guys,

I can’t seem to find documentation on how to boot from micro sd.
I wrote an installer image to the micro sd and wanted to boot from it via BIOS but it doesn’t show the sd/tf card as a bootable medium. Can somebody help me out? Please don’t recommend to just use a usb stick, for my project, it’s necessary for the rock pi x to be bootable from sd.

Thanks you in advance for your input.

As far as I know, only USB boot is supported. If the system is then installed on the internal emmc, this can of course also boot. But boot from SD / TF card is not supported.
At least that’s what other posts said