Looks like the Nand has been dumped for the retromini RS-90 which is a start i guess to getting opendingux on it booting from external sd card download below.
https://archive.org/download/retromini_nand
Retromini RS-90 Nand dumped
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the download isn't working :(
maybe a reupload?
Its only a matter of time.
hope there can be a custom rom flashed to the internal memory even tho i have a rs-97 i may get one of these if it can be hacked
is a amazing!