I wish I had a better sense of how these zero-click vulnerabilities work so I could get a sense of how to protect myself from them (you know, without giving in to Liquid Glass). Can they be blocked by an ad blocker? Are they blocked by any extant ad blockers? What about “Lockdown Mode”?

Note that this is 1-click.

0-click example: receive an MMS with a malformed image that exploits a bug in decoding

It's a watering hole attack. At any point your iphone sends an http request to a compromised site, by add, link, embedded, etc. your device will be exploited. there really isn't a way to permanently defeat this. We are about to see an explosion of novel attack types utilizing this exploit as their basis, you realistically cannot defend yourself against these without either updating or no longer using an iphone.

My understand is ad blockers only stop one class. Lockdown Mode is supposedly a major upgrade given all the underlying processes it blocks / slows.