Just focusing on soil moisture, if you want a sensor that produces reliable, validated data long-term (ie rather than a proof of concept or basic demonstrator), then maybe you need to be looking at established sensor makes. After all, measuring soil moisture is a well-established and widely-used technique in agronomy.
Probably the most familiar gypsum block sensor is the Irrometer make. For a better approach then Decagon is another well-known make and some Decagon sensors will also measure salinity and (IIRC) pH.
Serious agonomists are starting to recommend sensors like ‘Sentek Drill and Drop’ which can measure soil parameters like moisture & salinity at up to 12 depths simultaneously with a single sensor assembly (they’re available in different lengths from 30cm to 120cm with individual sensors spaced at 10cm intervals). These sensors are very clever and great for ‘Smart Farming’ but are also seriously expensive.