So i have a Medion P89637 with momentarily Debian onto it with a newer version of uboot. But i saw that Debian is quite messy and gets many errors wehn you install some packages. So i went into your forum and found a threath in how to install it on my box. But for that it seems you need the original u-boot and the original system. I wiped them both off. I found also the forum from that threath.
So my question is almost the same, is there a way to format the sata put rootfs onto it and let it boot whit maybe a command like dd or maybe extracting a tar archive on a partition called rootfs.
Since the previous owner tested something out i dont have backups, i created a bootable sata since the device boots from sata first and then from nand. on the sata there was a debian rootfs from here and with that i restored the nand using the uboot from here
The last post on that page is promising ( usb boot ).... although i'm not familiar with the 2nd and third lines.....
So If I were you;
Document the partitions currently on device
Decide whether to pursue safe ( dhcp-tftp or usb ) solutions VS mtd fixes
Then address the sata ( which would have needed some of two anyway )
If the uboot you flashed supports uEnv.txt in /boot on hdd..... you may have an easy path... ( which some of those links discuss )
All you'd need to do is;
a) built openwrt with a buildroot system, with disk drivers. ( suggest you setup one and get acquainted in your spare time )
b) get the kernel and dtb in /boot
c) get the rootfs next door
d) use Uenv.txt to set all the booting parameters
And you could have that on USB so as not to mess too much with the current setup....