I think it would be useful to have a public Phoenix/Liveview demo and testing site. Basically, each page would contain examples demonstrating best practices, useful techniques, etc. Aside from helping folks learn about ways to solve UX problems, this could support testing of accessibility, responsiveness, and other issues.
In order to make this happen in a sustainable way, we’d need to have some knowledgeable folks to vet submitted patches and generally maintain the site. And, of course, we’d also need a server somewhere on the intertubes. Any volunteers???