http://go7cnxivpns4x2trczyaabxwnrz7bwlxjiverkc32o4mjd5npjukpqid.onion/blog/2020-12-03-rescuing-n900.html
I decided I need to take a step back
and, instead of looking for what went wrong, look for how to do it right. I
started reading README from U-Boot sources. Fortunately I quickly found that the
initrd image needs to be converted as well. So I uploaded the converted initrd image, updated the boot script, booted the
phone and SUCCESS!!!