sysctl -a | grep mptcp
net.ipv4.tcp_available_ulp = espintcp mptcp
net.mptcp.add_addr_timeout = 120
net.mptcp.allow_join_initial_addr_port = 1
net.mptcp.checksum_enabled = 0
net.mptcp.enabled = 1
net.mptcp.stale_loss_cnt = 4
uname -r
5.15.0-25-generic