The link to the ebay auction you posted is for a 2018 model Genesis/MegaDrive Flashback. These are good systems. They run Genesis Plus GX on linux, rather than the custom android emulator of 2017.
A quick, easy way to determine the 2018 model by looking at the box is the mock volume slider on the left. The 2017 model didn't have that. Also, the box mentions an SD card slot, only available on the 2018 model.
The firmware on the AtGames website is for the 2018 model, not the 2017 model, and enables loading roms from the SD card.
The only critisisms I have of the 2018 model is:
- Master System and Game Gear roms are not yet supported from the SD card. The emulator can clearly run them, but the firmware does not reconize the extension. Hopefully a future update will change this.
- Boxarts on the SD card are not supported. I imagine it would cause moving through pages of roms to be a bit slower, but I'd like to have the option to add them.
- The sound of PAL roms is not handled correctly in the Genesis model. Hopefully this gets fixed in a future update.
Otherwise, the 2018 model is a very solid system.