Back from PostmarketOS stuck in debug shell

[toniox]

After playing with UBTouch I decided to try PMos too but unfortunately I didn't like it and I would like to go back and install UBtouch.

The phone is no longer reachable via ADB/Fastboot or even EDL by shorting the pins on the motherboard. I took it to an authorized Xiaomi center and they couldn't even flash the Android ROM again.

I believe the problem is due to pmos installation which requires loading custom u-boot, custom kernel boot partition and deleting the factory dtbo partition.

I tried a wipe from Recovery but I complicated the situation because I deleted the boot partition and I'm stuck in debug shell.

I'd like to know if it's possible to reload the boot partition using a micro SD or SSD connected via USB. The debug shell commands are limited, and I don't have the advanced experience to do so.

Thanks so much to anyone who can help.