The Fydetab Duo mainboard has a M.2 NGFF/SATA B key slot which is known to allow an upgrade/install of a 4G Modem card and antennas. There seem’s to be a M.2 SATA/NGFF B key slot, that may be used for the 4G Modem upgrade. Potentially it will work with SATA SSD storage drives as well? Anyone can confirm or has tested it? If it works, is boot from it allowed? That would allow to upgrade the Fydetab Duo with good performance and large SSDs for system/storage.
So, replying to myself, it seems that this slot only supports USB 2.0 devices, such as 4G Modem. It’s not a full use NGFF/SATA slot. Not even USB 3.0. Checking the available schematics (page 25), we can confirm it. Also, user @runaway97 confirmed on Discord to have tried connecting a SATA storage device to it to no avail.
Potentially a USB flash storage device may work on it. To be confirmed. But I guess in that case it will be limited to only USB 2.0 speeds, so not really that interesting.