My understanding is that the 2015+ Leafs support bidirectional Chademo, although I've seen posts of 2013+ and 2014+. If that's correct, I think a compatible V2G charger shouldn't require any special hardware or converters in the EV itself.
Details from Nuuve are quite light as they're still in startup mode. I don't know if they're only offering time shifting or if they also are providing disconnect/transfer for backups.
Having recently visited Nuvve's DC bidirectional installation, I know that they have used Hitachi CHAdeMO units with various older model Leafs. It will be interesting what they offer to the public. The AC units appear have the functionality of a charge controller - however going bidirectional certainly presents some interesting questions!