It's even relatively straightforward: start it up with a keyboard and video attached, enter the BIOS, and turn off the watchdog settings. I'd also recommend turning off the onboard eMMC altogether for the following FYI.

Just FYI: If you blow away the UGREEN OS off the eMMC, restoring it requires opening a support ticket with them, and it's some weird dance to restore it because apparently they've locked down their 'custom' Debian just enough for 'their' hardware.

As per someone on a Facebook group, "you CANNOT share the file as their system logs once you restore your device and flags it as used. It will fail the hardware test if the firmware has been installed again".