There have been many new resources popping up on the internet to help libraries deal with book challenges recently. We have recently identified a new site called Unite Against Book Bans (https://uniteagainstbookbans.org/). United Against Book Bans is an initiative created by the American Library Association to create a network of readers around the nation to advocate for libraries and provide support to those fighting challenges.
You can join their coalition on the site, get information on current and past challenges, and access some of their resources. Their resources include a free PDF toolkit, FAQ's, talking points, information on writing and distributing petitions, and much more.
Even if you are not facing a direct challenge at this time, it is a great idea to join the fight against them.