The bug in question was spotted in Chromium, not Google Chrome. That would leave Firefox as the only crossplatform and sufficiently up-to-date alternative. Not exactly "plentiful".
So there are definitely quite a few alternatives (the last two were obviously a joke though). Granted many are not as feature rich, but they'll still be HTML5 compliant.
Thank you for the correction on the Google Chrome/Chromium point though. Updated my post to reflect that.
Footnote: has anyone checked if this is a Blink issue or just Chromium? Because Opera, Vivaldi and other browsers use Blink but likely wouldn't have hotword. So that would be even more alternatives available.
This is a meaningless statement. HTML5 is a moving target. And on top of that, webpage design has deteriorated to the levels we saw around 2000 again: to be usable, your browser has to mirror the most popular engines well enough that sites work.
And if you want to get pedantic about HTML5 being a moving target, technically it's not. People often lump the other web front end components (CSS, SVG, EMCAScript, etc) under the HTML5 heading - those components will obviously have their own specification enumerations. Furthermore, a lot of the tertiary technologies that are a moving target are either experimental features / proposed drafts (ie not part of the final specification) or browser specific extensions. Most sites tend to avoid using these without fallback code for non-supporting browsers (demo sites being the obvious exception).
What about Midori (LGPL 2.1)? For some reason it's not available for jessie, but 0.4.3 is available for wheezy, stretch, and sid: https://packages.debian.org/stretch/midori
The latest version on Midori's site is 0.5.9: http://midori-browser.org/download/debian/
[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=786909#51
https://github.com/cisco/openh264/
Firefox downloads binaries from Cisco because Cisco can legally distribute this software in binary form in countries where H.264 patents apply, while Mozilla can't do so directly.
There was also a plan discussed to make it easy to automatically verify that the binary corresponds with the published source code, but as far as I know that work hasn't been done yet:
https://github.com/cisco/openh264/issues/893
Also, if you have the correct gstreamer H.264 plugin installed, Firefox should use that instead of downloading OpenH264.
