Is Citadel required in Istio 1.5+

The release notes for 1.5.x ( suggest that citadel, nodeagent etc are now not required, as this is handled by istiod. I’ve recently had certificate expiry issues, which I suspect could be due to still running nodeagent (a hangover from upgrading from an older version) - but the troubleshooting at states unequivocally that a healthy citadel is required.

So, is citadel in fact required or not?

@OliverI think the troubleshooting doc is just outdated need updates. Is that right?