As to soil samples, I use these: https://www.amazon.com/dp/B084TSNR79 (I have no affiliation with either the company or amazon).
I've had good luck with these but they tend to be on the pricier side, so I've been told.
MySoil - Soil Test Kit | Grow The... https://www.amazon.com/dp/B084TSNR79?ref=ppx_pop_mob_ap_share
I don't think it's high quality, but it's 30$