Although I can't directly answer your question, for me the opensource handheld scene did went through some phases. I have most opensource handhelds since the GP32 blu around 2002. In those days these handhelds were expensive: around the same price or even more than their triple A counterparts. So eventhough the GP32 was more expensive than a GBA, it could do a whole lot more! This situation changed with the GP2X as the PSP was quickly hacked and could also run emulators. I'm not sure but I think the GPWiz and Cannoo sold even worse and hence GPH stoppen making opensource handhelds altogether.
The situation with chinese handheldanufacturers is different, handhelds needed to be cheap so to my knowledge there were mostly NES on a chip handheld and GB hardware clones... until the Dingoo A320. And also this handheld was not marketet as an opensource handheld but a multimedia device (hence the FM recover, MP3 playback etc). Howerve this handheld did sparc a lot of dingux projects, like this website and eventually resulted in OpenDingux. Later chinese handhelds like the Dingoo A330, A380 and gemei a330 proved to be compatible so some extend with these projects. The GCW zero was a very exciting project which would change this: a high end opensource handheld with all the bells and whistles requested by the Dingoonity community and fully capable to run OpenDingux. I won't go into the drama that followed but most who did got the device loved it. I already did and I find it very sad that the drama surrounding the project also seemed to result in a stop/slowdown of the OpenDingux project.
However, both the original Dingoo a320 and the GCW Zero used the Ingenic MIPS CPU and the GCW Zero and OpenDingux project did result in a lot of freely available knowledge on how to build a OpenDingux handheld. And this resulted in the RS97. I think the success of the console was unsure during development, as it used the shell of the RevoK101 (a GBA hardware clone).
The succes of the RS97 sparked a avalanche of cheap dingux based handhelds (like the LDK and RS07, RS99, RS90 etc). Often these were not running OpenDingux bit with little effort could run a derivative of the OpenDingux firmware. Proven there was market for these handhelds and seing users wanted OpenDingux on these device Ambernic release the RH350 and the Bitboy team the PocketGo2. These devices were essentially GCW Zero clones with some upgrades/changes (second analogue stick, better screens, etc). These devices were expensive for chinese handheld standards but had the more powerful CPU and memory the GCW Zero also employed.
For me personally it WAS the RS97 which re-egnited my interest in opensource handhelds but I must admit I bought it together with the RS90, so I'm not sure which one came first...
Good luck with the video, I would love a in-depth analysis of the history of opensource handhelds.
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