I take your point. But how do you power this travel router? Also, does it have a 4G/LTE/5G SIM card? Otherwise, what is its modem; i.e. how does it route?
I realized late that you'd asked how it's powered. Most of them are powered from USB-C, so you can use a battery bank to power it or just plug it in.
It connects to wired or WiFi connections and bridges it to a separate internal network and routes all traffic across its VPN tunnel. These are common devices for security conscious travelers. Yes, some support cellular either directly or via USB LTE modems.