Cursory examination shows that this device appears to use an Ingenic MIPS jz47xx SoC, and is built on a truly ancient (~2008 !) linux base system.
Not bad for a device released in 2021... for about $1000, nearly double the price of its predecessor (the non-plus DTR1), also built on the same base system.
But assuming that Dethonray wants to assist in some way, the best thing they can do is to share the schematics for the device. The second best thing they can do is share the source code for the bootloader and linux kernel (including all device drivers) the device uses (Which they are supposed to be doing anyway as per Linux's GPL license terms). The third best thing would be to provide an SDK or something similar so that we can build rockbox to run on that base platform.
Their "UI code" is next to worthless for Rockbox's purposes, as we already have our own mechanisms for dealing with all of that.