Thanks for reaching out and for your interest in eero.
Unfortunately, eero will not work with just a hot spot as your main source. Either a modem or upstream router are required. If you have any other questions, feel free to give us a call at 1-877-659-2347 or email us at email@example.com.
Current cellular hotspots don't have Ethernet ports for the following reasons:
Space - there literally isn't enough room inside the cellular hotspot for the Ethernet port.
Power - Ethernet ports require power to run, and the cellular modems and wifi radios are very power hungry, about 3-5x more power hungry than a smartphone. There are some cellular hotspots in Japan with Ethernet ports, but they autoshutdown after 2 hours due to excessive power drain when the Ethernet port is used.
Heat - cellular hotspots run very hot while in use, frequently needing 15-20 minute shutdown periods after several hours to cool off before being rebooted.