I will start testing very soon with an AudioMoth Dev unit to record signals from tiny ground arthropods. The signals are very weak and very low frequency (some audible, some not), so I will need to preamp them by a factor of 100 (+40dB) or 1000 (+60dB). I will use a shielded 10 µΩ piezoelectric film as a sensor - https://www.te.com/usa-en/product-CAT-PFS0010.html.
Andy provided very valuable information about the device gain values in https://www.openacousticdevices.info/support/device-support/calibration-for-sound-pressure-level-measurement/p-1/dl-60800bbcbb7c0c001500dc98.
However, I don't know if it is possible to modify the firmware on the device or if there would be any complementary software or hardware solution for me to achieve the goal.