There are posts on the forum that states that there are ideas about getting non-Hak5-devices, such as the Raspberry Pi, connected to Cloud C2. Those posts were back in late 2018 though, but I guess there's a lot of stuff going on in the "Hak5 factory" that occupies valuable dev resources. Most likely not a top priority compared to the management of the Hak5 ecosystem, but totally possible to happen I guess.
In the meantime, a Raspberry Pi can still exfiltrate loot to Cloud C2 if using Hak5 devices as "loot shippers". It is possible to use at least the LAN Turtle, Packet Squirrel and WiFi Pineapple for such purposes. Collect the loot desired using the Raspberry Pi, ship the loot to the Hak5 device and then let the Hak5 device upload the loot to Cloud C2.
I have made example bash code available for both the Raspberry Pi and different Hak5 devices on my GitHub. https://github.com/chrizree/LootShipper