Thank you very much for your interest in NSPanel Pro.
We were too busy to develop v4.0.0 firmware and later fix it through v4.0.1~v4.0.10 
so we havenāt published formal release note. From the feature set point of view, v4.0.x firmware is basically the same as v3.x firmware. One could even argue, v4.0.x firmware lacks several major features of v3.x firmware, for example, Web Shortcuts, Open API.
If you are curious where NSPanel Pro is headed, please take a look at NSPanel Pro Roadmap and Co-Created Future.
Are there any plans to upgrade the Android version? I asked SONOFF about a year ago as panels are currently on Android 8 IIRC which is a huge security issue given theyāre on WiFi and connected to the cloud, and they mentioned it was being worked on. Thereās plenty of work being done on projects like LineageOS to keep older devices supported that could be piggy-backed off of
The current plan regarding the underlying Android 8.1 OS is to open source it. After that, we may try to upgrade to newer Android OS. But Android OS is a huge system, and we rely on SoC vendors to provide necessary support. Most of the time, we have to use new generation of SoCs to run newer Android OS.
LineageOS is great. I love it, and I am using it. But as you can see on device pages (for example, Xiaomi Mi 8 Lite) of LineageOS, many devices have lost the opportunity to further upgrade due to the lack of support from SoC vendors.