Something maybe a bit related.

I just had 25Gb/s internet installed (https://www.init7.net/en/internet/fiber7/), and at those speeds Chrome and Firefox (which is Chrome-based) pretty much die when using speedtest.net at around 10-12Gbps.

The symptoms are that the whole tab freezes, and the shown speed drops from those 10-12Gbps to <1Gbps and the page starts updating itself only every second or so.

IIRC Chrome-based browsers use some form of IPC with a separate networking process, which actually handles networking, I wonder if this might be the case that the local speed limit for socketpair/pipe under Linux was reached and that's why I'm seeing this.