What is this cassette / hanger combination please?

[Squaredisk]

Here is a more recent version of the same. Lots of pics to show how it works.

https://bikerumor.com/ib17-wild-mandaric-standard-21-5-concept-runs-the-cassette-outside-the-frame/
For some reason i think the bike in the OP actually might be a Motobecane.

@Frankenorange that is interesting. The owner has removed the sale images now - maybe we will never know!
I read about Bivalent hubs which were a vintage thru-axle design.

 

[sunympholepsy]

Interesting about the 8freight! (had a Google of it)
The tube decal makes you say Vitus 788?

Just a guess. It looks to me like a Vitus or TVT tubing decal… Not that’s that relevant. Just thought it might help narrow down the search slightly