Valve Steam Deck
Just in case anyone is Ctrl-F-ing this for NVMe M.2 M2 SSD upgrade slot support for the 64GB eMMC version, apparently, the base model does indeed have the NVMe SSD slot like the higher versions according to this:https://twitter.com/RobotBrush/status/1416150442841628677which would appear to imply you can upgrade the 64GB eMMC with a NVMe SSD by yourself.