The current generation C6 is directly available in the following shops, which is why a reservation is unnecessary at the moment. I.e. just order there directly:
- eBUS Adapter Shield C6 at Elecrow
An enclosure is available there as well as option. - Partly it is available here as well: eBUS Adapter Shield C6 at Berrybase (without enclosure) or with enclosure
- The Stick Edition including enclosure is available here as well: eBUS Adapter Stick C6 at Elecrow and eBUS Adapter Stick C6 at Berrybase
The adapter C6

the Stick Edition
and the adapter v5

allow being used via USB, WIFI, Raspberry Pi (excluding the stick),
or Ethernet (USR-ES1 module NOT included!).
Comes with an eBUS plug but without a USB cable.
For Ethernet, an additional module is needed that is available separately, e.g. as option at Elecrow. Or see the links in the docs.