Milkwood
Milkwood offers a wide selection of resources including articles, books, and online courses. be sure to check them out https://www.milkwood.net/
Forest Fungi
has been around 10+ years and taught a lot of the long time growers in Australia check them out https://forestfungi.com.au/
Mycelia.be
if you are serious about starting a commercial farm then go no further than Mycelia in Belgium a week long course that covers everything https://mycelia.be/