I've been trying to find it for a week now but I don't seem to have any luck so far. I had seen a video about it a couple years back from a brittish YouTuber who mainly reviews DEs, although his name slipped my mind.

It is a very minimalist UI with not much customisation apart from dock size, transparency and positioning, it is niche and not an extension or customisation of another DE, and I believe it may still be in beta, although I'm unsure.

Also I apologise for the image quality, it was the only one I could find. If anyone can identify it I would really appreciate it, although I understand if you are unable, thanks.

EDIT: Also I checked if it was Orion OS or other OS names in the text but none of them matched.