It is not possible to play videos attached to this Bugzilla. This has been annoying me for many years and we probably have another bug report for this somewhere, but I cannot find it. For example, try loading this video in Epiphany Tech Preview with WebKitGTK 2.42.1: https://bug-263709-attachments.webkit.org/attachment.cgi?id=468346 You'll see a broken page with no video. The inspector console contains an error: [Error] Failed to load resource: Plug-in handled load (attachment.cgi, line 0)
WebKitWebSourceGStreamer.cpp:1058:responseReceived:<source> error: R2: Received unexpected 200 HTTP status code for range request
Looks like a dupe of #221622
*** This bug has been marked as a duplicate of bug 221622 ***