Hi @phil31 ,
For now using class c is a bit tricky :D, not impossible.
Your Gateway, the LAIRD RG186 comes with LoRa Gateway-bridge preinstalled after version 188.8.131.52. You can read more about it here LAIRD Lora Gateway-bridge. This means you only need to connect it to the MQTT broker.
As @Fomi mentioned there is an of Ubuntu with loraserver.io built-in. You can find it here LoRa Server OS
In case you really want to try working with the TTN V3 stack, at least for now you have to do it on a local server (the cloud platform does not support it yet). You can find the repository for it and a tutorial in this link TTN V3
And as you can probably already see, that is why the RAK831 is so popular. You can run it all locally since it uses an RPi at its core. You can have the servers (LoRa or another type), we also run our database (we use InfluxDB as it is compatible with loraserver.io), graphical tools (we use Grafana), etc.
So lots of options to choose from. I myself went with everything on the gateway, perhaps you go another route and share your experience.