In August we finally finished the development and released StreamTest on Google Extension store. So you can now download it via the link: https://chrome.google.com/webstore/detail/streamtest/apmgkjaoljlahcldcoekghdngcbceebf?hl=en
We also made a complementary instruction / article with detailed info about all the characteristics and more. Check it out: https://forasoft.com/blog/article/how-to-test-webrtc-stream-quality-1231