One other item that is hopefully listed in the Acorn store are the PCie adapters mentioned in the first post:

"I am also pursuing making available well priced options for individual PCIe x4 to M.2 M-key host boards (these are broadly available for $10-15), as well as Quad-M.2 PCIe switched and Bifurcated x16 host boards for those who do not have the available M.2 M-Key slots or require up to 240MH of acceleration."

This way, the user gets a tested, Acorn compatible, hardware solution .