Unbricking an UniElec U7621-06

I was trying to flash a new firmware on a U7621-06, but I accidentally wiped the u-boot partition. Which methods can I use to restore the u-boot? Do I need JTAG?

if uboot's gone, you'll need JTAG.

I have little experience with it. Do I need a specific JTAG connector for these devices?

Here are openocd scripts and instructions specific for mt7622 with a mt7621 config file on directory up

I dont know if this will work for mt7621

Here some mt7621 related JTAG notes from the vonger.cn



some more notes (use google translate to get it to english)