Anyone figured out best way to detect rain?

Yes, you can use the driver I now look after:

Yes and no.... You need something to act as a gateway, which will often be the kind of device you showed, but some of the displays EcoWitt sell (not all, I believe) can perform the same function, but check the displays features before purchasing.

The gateway is the device that the sensors send their readings to and it's the gateway that handles sending that data on to Hubitat and other destinations that you choose.