Wait a minute, what does the FPGA have anything to do with the 48 kHz (not hertz) resampling rate, which is anyway bypassed by the iBasso implementation? Resampling to 48 kHz is not a new thing in Linux kernel based systems - even on desktop Linux (Gnome, KDE) PulseAudio by default does resample - PulseAudio is now replaced by PipeWire and it also does resampling.
I am not an Android programmer (but I did Linux kernel development mainly for video including systems running algorithms on FPGA), but for sure all PipeWire, PulseAudio and the Android audio infrastructure sit on ALSA, which probably goes through the I2S driver of SD660, and which then goes through the FPGA, ending up at the door of the DAC and I don't see how you bind the resampling of the Android audio infrastructure (which is anyway by-passed) to the FPGA arbiter.
https://www.head-fi.org/threads/iba...irmware-2-6-2021.943221/page-58#post-16061916
The FPGA replaces the XMOS chip and does jitter correction - so I don't see any DSP being done there. But I wonder how did you relate the crosstalk to a digital component. Crosstalk interference is an analog domain problem, not digital which the FPGA is, so how do you expect the FPGA to solve interference? And how did you come to the conclusion of "much better", "snappier" firmware functionality, because at this level of a high performance controller, I don't see the possibility of a human brain detecting the difference.
Reverse engineer? What? I do CUDA programming which has an open programming interface based on C/C++ and anyone can download the CUDA SDK and start programming. There is absolutely no reverse engineering needed - even more AMD has ROCm which supports CUDA, compiled via LLVM.
What is extra bells and whistles? DX300 is a pure audio device. In another post you mention OLED display and complain about bells and whistles? I had other "portable" DAPs, and I have not so far seen anything driving my T+A Solitaire P and P-SE as good as DX300. It is very powerful and can drive such headphones to very good levels for a DAP. Let us know what those "a lot of great choices" are, so that we also can benefit from your list of great choices.