It is a strange behavior, but normally chinese companies erase the chip’s name used on their products:
Trying to protect your product using obfuscation is not a good idea, soon or later someone will figure-out it. Actually I figured the chip used on this product in less than 5 minutes (AFAIK I was the first one to figure out it).
They are using the MVSilicon BP1048B2. I also found the datasheet (brief-sheet), but didn’t found the SDK for it and how to program it.
This chip seems mostly used on Audio Sound Bars and other audio bluetooth products.
This chip is very powerful, seems a good candidate to run NuttX RTOS, see:
Update: Aaron Christophel (aka atc1441) found the SDK for this chip on github:
https://github.com/leadercxn/bp1048_sdk_v0.1.12
Alan C. Assis 
Look at the website in Chrome with translate turned on ( http://www.mvsilicon.com/pro/newic.html ). Selecting ENGLISH on their website removes a lot of content. Once there you can navigate to that chip where shows high-level technical information and says “Software Development Support, SDK includes various codec and audio processing algorithms, Examples and many middleware, Eclipse based IDE and GCC compiler, Support FreeRTOS, Full C programming, easy code porting.” I would contact their technical support and see if they will provide the SDK. If you tell them your intent of developing a port for the Nuttx embedded system OS I suspect that they will provide it. Technical support: email jack@mvsilicon.com Phone (021) 68549851, extension 106 Jack
Thank you celem! I discovered that Unisound also has another chip with same core (NDS32 V3S) and people from Ai-Thinker released much information about it, including the SDK, Flash programmer, OpenOCD debugger, etc. I will ping MVSilicon anyway. Let’s see!