Using LXCs I made sure the kernel has that module and that it is in fact available in the containers. Whatever is available on the host is also there in the containers. 1 kernel only.
But modprobe does not work in the container, what does that mean regarding the script?
modprobe: FATAL: Module tcp_bbr not found in directory /lib/modules/5.4.0-52-generic
Thanks in advance for that info!