While I agree with others pointing out the oddity of a portable server in general: this sounds like a great use-case for a laptop.

Built-in battery, wifi you can broadcast out as a hotspot, and it even has a display/keyboard/mouse for troubleshooting!

An older laptop with the optical drive stripped out could have a 2.5” 5TB HDD in addition to the boot drive for some decent mobile storage.

FYI Nexctloud supports webdav.

I run it and mariaDB in docker and they run perfectly when left alone, but everything breaks horribly if I try to do an update. I recently figured out that you need to do updates for NC in steps, and docker (unRAID’s, specifically) defaults to jumping to the latest version. I think I figured out how to specify version now so fingers crossed I won’t destroy it the next time I do updates.

Sometimes it’s configurable through the web interface, sometimes it requires a call to the ISP if you’re using their locked-down modem.

I’m not familiar with IT norms in China though.

What? I can’t hear you over that airplane.