Test it, it looks to fit but others haven't had theirs work.
Sorry, I don't have an Acorn yet but I wanted to see if I could use an adapter if I bought an Acorn. I had read multiple pages back that someone asked the question but I didn't see a reply and I find the Discord page virtually impossible to read for more then a few minutes. I might have to play with screen settings or something but it looks like a jumble of dense text and not a readable narrative.
CreativeReef
I gotcha, so someone already has tried, I bought a cheap AliExpress one but it had the key the wrong way and the heatsink would be facedown making it impossible.
It's worth a shot for testing but not for buying, I'd hold of but pcie adapters work great and slide into the PC well.