Thanks so much for sharing these links! We're working on expanding our resources for soil sampling, but you might be interested in some of the work that @jjcreedon is doing with a soil kit she and some of her partners at developed as part of their advocacy work in Western New York (also coming soon to our online store). You can read some more about their methods at the Soil Sampling Toolkit.
Can you say a little more about what kind of soil sampling information you're looking for? In the US (where I am based), a lot of our sampling methods are informed by EPA protocols-- these are procedures that might allow someone to pursue enforcement or regulatory action if a sample is found to contain contaminants traced to a polluter, but obviously the methods vary depending on the nature of the concern (and enforcement is subject to all kinds of additional factors)
Soil sampling has certainly been a part of work throughout the Public Lab community over the years, but a lot of the information and resources on the Public Lab are folded into larger project descriptions. You might be interested in some of our resources on Turbidity Testing, some of the work our partners have been doing on [Frac Sands (https://publiclab.org/wiki/wisconsin), or these posts about mountain top removal, this post about a method for conducting a terrain survey, or even some of these resources about landfill --all pretty different issues revolving around soil.
That said, this is an area we're working to develop even more resources in this area! We're currently looking for a fellow who can help to build upon some of our soil resources (job description here), which may be of interest to some in your community.
That said, I'm really looking forward to reading more about your work and hope we can connect some more on this topic-- I think our community members would be really interested in the work you are already doing. I'm especially interested to see that you've been doing some microscopy with soil: this is something we've been trying to learn a little more about as well!