finally got hold of one of these.... a Diium D-R28S aka D28S aka D-28S
it's a mini emulation handheld!
it has a 2.8in screen with an RK3326 CPU, that CPU is very common these days but its still quite rare to see it paired with a smaller device with smaller screen and no analogue sticks. and it looks very cool imho
The OS is on internal EMMC here, and it's a dubious version of EmuElec. It works okay enough out of the box but I haven't found a way to access the EMMC which means customisation is limited. And another owner has managed to get it stuck in a bootloop by trying to change the theme
It probably is able to boot from SD though since the SOC can usually do that as standard. So a custom OS is probably possible but it's unlikely any existing builds will work since they have to account for the screen and controls. And who knows if any devs will take interest in it
On the hardware side the screen is nice and it feels well built but i'm not enjoying the controls, the D-pad doesn't have much pivot & gives false diagonals, and the face buttons are too small and far apart. So even if the OS issue can be solved this might be kind of a miss sadly
It's frustrating though because this same company previously made 2 devices with IMO perfectly good controls, the D007 and D-R35 Plus, they had decent d-pads and big chunky face buttons so its weird they reversed track on something they were actually doing right
RK3326 devices are pretty widely supported with custom linux based OSs & the common setup for them is to have 2 MicroSD card slots, one for the OS and one for games
This does have 2 slots. But. However. It only came with a card in slot 1, which is full of ROMs and not much else