Hi,
I have a really weird issue with my Nextcloud 12.0.2 instance installed on Ubuntu 16.04 and served by nginx 1.12.1.
The main webpage (which you can find here [this](https:// cloud.gabrielelucci.xyz) btw) won’t load on Firefox. Works perfectly on any other browser / device I tried, but it just won’t work on Firefox 55 or even Firefox Nightly 57. I just see a blank page, no response header and no error message. Does anybody experienced something similar?
I’m guessing it has something to do with http2, because if I disable it in nginx or set network.http.spdy.enabled.http2 Firefox flag to false, it will actually work and load the page just finevia http/1.1. But why? Other sites (for example duckduckgo.com) using http2 load just fine.
The configuration line was telling nginx to serve the broken header Strict-Transport-Security "max-age=15768000; # includeSubDomains; preload;". Most browsers do not complain for some weird reason, but curl and Firefox get (reasonably) mad.
Thank you @tflidd, debugging with curl was really key.