I posted some additional details of our testing on https://serverfault.com/questions/942863/safari-fails-to-load-some-resources-over-http-2-with-apache. We were unable to figure out a way to disable http/2 just for Safari and came to the conclusion it wasn't possible.
We are also able to reproduce this issue. We did several days of testing
trying to pinpoint the issue and also determined it was for sure http/2
with Apache 2.4.25 on Debian Stretch only, and only a problem in Safari.
We were unable to reproduce on other versions of Debian/Apache, with
http/1.1, or with any other browser. We were able to duplicate as far
back as Safari 9 on Mac and iOS 9 Safari (we didn't have older versions
than that available to test). For now, we have disabled http/1.1 (better
to load at all than to sometimes load faster), but this does hurt Google
page speed/Lighthouse scores which in turn hurts search rank so we hope
a solution can be found.
- Bug#915103: Apache2 HTTP/2 connection problems with Safar... Josh Janusch
- Bug#915103: Apache2 HTTP/2 connection problems with ... Patrick Matthäi
