How can I get rid of persistent zombie tabs in iCloud Safari?

No such thing as.plist that I can see.

Support wanted me to do the trick where you turn off tab syncing on both devices and clear history on the one with the zombie tabs before re-syncing. I've tried that numerous times, and while it usually does the trick, it isn't getting rid of this pair of tabs.

I've also tried renaming the whole Safari folder at the location you mention, and I thought that did fix it, but the tabs still came back.

Yeah, I've tried that many times.

I think I've fixed it by deleting the CloudTab.db files at ~/Library/Containers/com.apple.Safari/Data/Library/Safari, which was a recommendation I found on some support pages