Dont forget:

https://myip.speedtestcustom.com/

https://www.bing.com/widget/t/speedtest

https://www.speedcheck.org/

https://gospeedcheck.com/

https://speedtest.xfinity.com/

In case it's not obvious, there's lots of *.speedtestcustom sites. They're a "private label" version of Ookla's speedtest.net without the ads. I think the backend is the same.