Inseego Skyus or Digi Digi TransPort are good 4G options. We use the Ethernet capable model to allow instant 4G fail-over to WAN2 and provide more specific adjustments if needed, rather then using it as a USB cellular fail-over.
Highly recommend using embedded SIM models if you have them working in your region. As noted earlier in this thread working alternative is Skyus DS but its "yet another box" to your network.
USB dongles are a pain to handle with overheating etc.