Looking good!
No errors in Google console: https://search.google.com/structured-data/testing-tool/u/0/#url=https%3A%2F%2Fmeta.discourse.org%2Ft%2Fdiscourse-2-2-0-beta8-pwa-error%2F106581
Preview (no idea how long this link will be good for): https://www.google.com/search?prvw=AHHjJUO7WRbGaPHHtHMRJbfhShyOyUOOHQ&q=previewid%3A4f63e9e8-25f5-420e-8ff3-0e8d720221cc&useragent=Mozilla%2F5.0+(Linux%3B+Android+7.1.1%3B+Nexus+6+Build%2FN6F27M)+AppleWebKit%2F537.36+(KHTML%2C+like+Gecko)+Chrome%2F66.0.3359.106+Mobile+Safari%2F537.36&filter=0&gws_rd=cr&newwindow=1&igu=1