Why you dont use this easy guide ? You must only upload url adress here from logging. Now you have booted last updated system with older dtb. It would be maybe usefully see logs from this case.
https://wiki.coreelec.org/coreelec:debuglogs
For your issue with dtb dont need maybe uart usb adapter. And how you will put on board without compatible pins on minix box? In past was special sdio debug board for this: CoreELEC Team SDIO Debug Board
I found something with support of sdio debug: Amazon.de …but only CE team know say if is usefully or not.