The xDot and mDot are LoRaWAN certified end-devices. They can connect with any LoRaWAN Network. By default the latest firmwares should be able to join a public network after setting the AppEUI/JoinEUI (AT+NI) and AppKey (AT+NK).
Can you share any of the multiple sources so we can work to correct this?
There is a private LoRaWAN MTS specific network mode with different default join delay of 1s for all plans and differing downlink channels for US/AU channel plans. This would only work with Conduits, but it is no longer the default.