@cR0w some Kagi-ing suggests PAN-OS zone protection defaults to following the global MPTCP setting, and the global setting defaults to stripping the option, so MPTCP connections are downgraded to plain TCP.
F5 BIG-IP's TCP profile mptcp value defaults to disable, which excludes MPTCP through the virtual server.
NetScaler's TCP profile mptcp attribute defaults to DISABLED. (1/2)