>It seems that we now have a clear proof that it's actually helping versus certain type of attacks (including source-code supply chain attacks).
So would have a vpn or using a bastion host with a custom non standard ssh implementation...
At some point you have to make the choice to not implement a security measure and I would argue that should stop at vpn+standard software for secure access.
If you are a bigger company, probably add SSO and network segmentation with bastion hosts and good logging.
Port Knocking doesn't add any security benefit in the sense that there are known non avoidable security risk aka your transmit your password(knocking) in clear text over the network.
You also add another program with potential vulnerabilities, and as port knocking is not as popular as e.g. sshd, wireguard, maybe it gets less scrutiny and it leads to a supply chain attack?
Security measures are also not free in the sense that somebody has to distribute them and keep the configuration up to date, even if that person is you, that means syncing that connect-to-server-script and keeping it in a secure location on your devices.