With M.2 drives being so cheap these days. In fact cheaper in bigger sizes than either micro SD cards or normal SSDs. Why has no one designed a board with a M.2 slot? I know Mister is never going to use any of the available bandwidth but that's not the point. It's all about price, convenience and keeping a small footprint without any cable mess and external drives hanging on.
Perhaps a new USB Hub board design with a M.2 slot on it?
I would imagine it's because the addition of a SATA to USB controller along with the M.2 connector with would push up the component cost and add needless complexity.
USB M.2 adapters are cheap as chips and every board out there has plenty of USB. If you're popping this in a mini-ITX case there's usually ample space to tuck the drive away.
Might also be as simple as reversing an USB port on the board in-ward.
you'd probably need to wire up a nvme / s-ata controller to the DE10 nano, total cost would probably exceed it's purpose.
usb would be the cheaper solution, but no one os holding you back to do it yourself?
i believe the MiSTer multisystem is open source now, so there's a starting point right there.
shouldn't be too hard to wire it up right?
i look forward to your endeavors, keep us posted!