These two diagrams show drafts of analogue data acquisition modules. The first is a 8 channel 24bit @30Ksps while 2nd is a 16 channel 12bit at 2,5Msps.
The ADS1256 is available for ca 5.- USD and provide 8 channels with 24 bit resolution at a sampling speed of ca 30ksps. This is very good for an ADC with this high resolution.
The faster ADC technique is achieved by using the ADC’s integrated in STM32 directly. These are 12 bits, but have a much higher sampling rate capability (2,4Msps).
I am not sure if I want to make both boards + I need to dig in a bit on analogue scaling & calibration options. I also need opto isolators that have limitations of their own. I also have the issue that the higher frequency of the 12 bit is of little usage + 12 bit resolution is a bit low for sufficient accuracy. Assuming I have space I could actually extend the 24 bit board with a few faster 12 bit channels as well.