As far as I know, BBR3 is not in the mainline Linux kernel, so obviously it will not be in Debian by default.
From https://groups.google.com/g/bbr-dev/c/i-sZpfwPx-I/m/0jmNry0A... :
> To make sure we're all on the same page: currently the TCP BBR code in Linux is BBRv1. We are working on getting BBRv3 upstream into Linux TCP.
> BBRv1 is definitely not ready to be the default on any Linux distribution. Whether BBRv3 is ready to be a distribution default is arguable.
Wish it was a klm. The FreeBSD model is (in that regard) easier to work with, from the Netflix stuff.
I'm running somebody's rebase tracking things. 6.13 I believe. Worked on one box, not on another. Oh well. Doubly irritating is that the sysctl only flags bbr not which version.