Infrastructure

Currently (2017-12-31) only few backends support HTTP/2 protocol on TDF infrastructure:

https://tinderbox.libreoffice.org
https://opengrok.libreoffice.org
https://api.libreoffice.org
https://dev-builds.libreoffice.org

Note, that the link from devcentral to dev-builds.libreoffice.org is wrong:
http://dev-builds.libreoffice.org/cppcheck_reports/master not https

All other TDF backends don't support HTTP/2:

https://devcentral.libreoffice.org
https://wiki.documentfoundation.org
https://ci.libreoffice.org
https://bugs.documentfoundation.org
https://help.libreoffice.org
https://translations.documentfoundation.org
https://perf.libreoffice.org
https://lcov.libreoffice.org
https://crashreport.libreoffice.org
https://gerrit.libreoffice.org
https://ask.libreoffice.org (there is no link from devcentral for ask)

FWIW: on nginx, these lines would enable HTTP/2 protocoll:

[...]
listen 443 ssl http2;
listen [::]:443 ssl http2;
[...]