Setup the flags in sysctl.conf and reload sysctl.

echo 'net.core.default_qdisc=fq' | tee -a /etc/sysctl.conf
echo 'net.ipv4.tcp_congestion_control=bbr' | tee -a /etc/sysctl.conf
sysctl -p

sysctl net.ipv4.tcp_available_congestion_control
sysctl -n net.ipv4.tcp_congestion_control
lsmod | grep bbr