Not sure if this helps, but e-sims are extremely cheap and can be set up on the go through an app these days. You could get a 5g plan in the area with bad internet and use it as a hotspot to download content to your other devices. I use Nomad, but there are a lot of providers with plans that are unlimited or pay by the gig—all affordable with time periods as short as 7 days.
A $10 solution, in a pinch, is a good choice.
It says right above that box that it requires the WHOOGLE_CONFIG_PREFERENCES_KEY or that option will be ignored. My guess is that you have to manually edit some config file to turn that key on, or generate an encryption key yourself that you provide through editing a config and adding it to that line.
Edit: you probably need to add your own domain or IP as the root URL too.