Another way is Termux your phone with Debian (https://wiki.termux.com/wiki/Debian) then SSH in to use it for building that flatpak USB stick. Basically, you're making your phone into a Debian OS to operate as supply chain dept.
Flatpak is an autonomous offline package manager. They actually thought this out exporting to USB device/Single bundle file.
You're asking a solution against the government's decision - it is never easy. Like it or not, workaround is illegal.
