How do I choose the type of demoboard being compiled?

I would like to understand however in which file to compile I write that the compiler “must choose” imx6ull-colibri-wifi-eval-v3.dtb and not imx6ull-colibri-eval-v3.dtb. For example, in my case the colibri iMX6ULL WB module is installed on an ASTER demo board and not on a Colibri Eval demo board. I noticed that there is a file called imx6ull-colibri-wifi-aster I have to use it, if so how? Thank you and sorry for all the questions but I’m inexperienced

How about setting the fdt_board U-Boot variable?

Colibri iMX6ULL # echo $fdt_board

The module variant (e.g. Bluetooth/Wi-Fi or not) is automatically determined by U-Boot.

Colibri iMX6ULL # echo $bootcmd
run ubiboot; setenv fdtfile imx6ull-colibri${variant}-${fdt_board}.dtb && run distro_bootcmd