I compiled from source (“git clone -b coreelec-19” then “make”) and I put the resulting img file (CoreELEC-Amlogic-ng.arm-19.1-Matrix_devel_20210419134403-Generic.img) on my sdcard.
However, the device_trees folder doesn’t contain anything related to KIII Pro. The page CoreELEC - Device Trees says that the DTB for Mecool KII Pro should be gxm_q200_k3_pro but actually there is no gxm DTB file in the device_trees folder.
Anyway I managed to find the following file in my build folder :
So I tried it (copying it to the sdcard and renaming it to dtb.img) but it hangs at boot (at the boot logo).
Could you please tell me where I can find the right DTB and how come gxm DTBs are not available in the device_trees folder ?