@guillaume_smartcitiz it is clear that there is a lot of work done on this project.
And SCK works, generally speaking. But if you look closer, several aspects are far from robust and optimized.
Apart from peripherals declared as working but not working at all, like the OLED display, web site really unfriendly and impossible to use on mobile devices, and other issues that could be considered not critical, the single most important flaw of present firmware is calibration. It is simply not foreseen, at all.
As most measurements depend strongly on boards assembly, position, and enclosure, you are granted that measurement accuracy is much lower than It would be if you could load correction factors for your specific setup.
With 2.1 Kit, you easily can have 1 °C of error in temperature, and 10 points error in humidity, depending on setup. As these values are used to correct other measurements, for example TVOC measurements are corrected for humidity, and it is a strong correction, also those measurements are messed and unreliable.
I spent days to find the best layout which was able to provide, at least, a correct temperature measurement. No way for humidity, it was wrong in any case. If you look at the code, you find that there are fixed correction factors inside, not parameters, hard numbers written in the code lines, and to change them you should modify the code and then recompile the whole firmware! Those correction factors are probably valid only in a single situation, with a particular enclosure, but this is not documented at all! I cannot imagine a worst way to manage this aspect.
Just give the user the possibility to calibrate the kit in his application setup, at least temperature and humidity, modifying a text file to be loaded in the SD card, and the quality and usefulness of the thing would have a huge improvement.
I suspect that all those offline and probably unused kits are simply kits that gave unreliable and wrong measurements, impossible to fix for the average user, interested in environment monitoring but not willing to mess with firmware and development tools, so they were disconnected and left in an angle.
About open source and to be active. Well, I wrote some software for Arduino using its IDE software, but never used the tools that are mandatory to change SCK firmware. If I mess it and the kit does not work anymore, who will help me? Looking at the level of support offered by this forum, I am not risking to brick a product that costs 150 Euro. I am sure that many other people think the same.
It is really a pity because the hardware itself is really good.