Trying to add something inline between my cable modem and my wifi router (google wifi) that would detect when my internet goes down and would automatically switch to using a LTE dongle (or even 5G if those exist yet).
I guess I want at least 2 Giga ports and a USB 3 for the dongle. I don't need wifi for this application.
Hopefully I can find something in the $50 range.
A 5G cpe (search for oppo cpe t1) is about 400 bucks. It has 3 gig ports and WiFi 6 (ax) but no chance for openwrt.
In your price range you can only get a mt7621 device with 5 gig ports and USB 3 (search for dlink dir860l only B1 hw)