This is misinformed and dangerous advice, MPTCP is not a requirement. You would need to block all TCP packets with any IP options set to fully mitigate this. Thankfully iptables/nft can do it.

Yup, was nice to see on my gentoo system. And then this amusing tweet from the grsecurity guy: https://x.com/spendergrsec/status/2116602388471758887