Set up a giveaway on Goodreads?
https://www.goodreads.com/giveaway/show_create_options
Offer it to members of permaculture groups on Facebook:
https://www.facebook.com/groups/529004747124365/
https://www.facebook.com/PermacultureGuild4/
https://www.facebook.com/groups/340508956666317/
et cetera
Send copies to book reviewers
Give a lecture on Zoom, and choose someone from among the attendees (random drawing from people that ask questions)
Ask a local CSA to offer the books as a low-cost add-on to subscription boxes (allow the CSA to collect a little bit, so compensate for their time)
Find local eco-newsletters (like
https://theaustincommon.com/ ) and offer them (A) a review and/or (B) a couple of copies to give to new subscribers
Offer them to people giving permaculture classes