Speedtest uses HTTP 1.1 only?

I took a look at Firefox's developer tools network tab while the speed test was running, and I noticed all the requests were being done over HTTP 1.1, even though I had HTTP 3 and HTTP 2 enabled.

When disabling both HTTP 3 and HTTP 2 in Firefox so it only uses HTTP 1.1, most of my issues browsing and downloading from other CloudFlare-hosted sites disappear. For me, transfers suffer most when transferred over HTTP 3, which is enabled by default. HTTP 2 is less affected and HTTP 1.1 feels fine.

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I copied this from https://github.com/AKVorrat/Netzbremse.de/issues/12, but I can see https://speed.cloudflare.com behave identically, with all `__down` requests (and other requests to `speed.cloudflare.com`) only using HTTP/1.1.

The speed test regularly (but not always) saturates my connection (Deutsche Telekom, AS3320), only rarely dipping into the low Mbps, while CloudFlare-fronted sites using HTTP/3 or HTTP/2 often crawl at sub-megabit speeds.