Mail rules not syncing between Mac and iPhone

I've noticed this behavior since approximately Catalina and chased it with Support for years. According to multiple Senior Advisor contacts as well as their attempts to get an Engineering discussion of the issue, the nearest we've come to an answer is that Mail doesn't do that (any longer).

To be clear, I am writing of how MAIL RULES are applied/synchronized across devices, not of the email sync functionality. If you see emails in different folders on your iPhone and Mac then you probably need to toggle iCloud Mail off/on on both platforms to get them to synch the emails.

Mail Rules are set and applied only two places, iCloud.com (server level, but ridiculously simplistic) and within the Settings of the macOS Mail app. There are no Rules that can be set or applied on iOS or iPadOS devices. And the Rules you set up in macOS Mail Settings DO NOT SYNCHRONIZE ACROSS ICLOUD. Once the emails land in a folder, their existence and disposition (which folder, deleted, etc.) is synchronized via iCloud and should end up in the same places on all platforms.

The problem, as I see it, is that whichever platform "receives" the emails first decides where they end up. If you have Rules set in iCloud.com Mail, those are applied and maybe your macOS Mail Rules will be applied. If you don't have rules set in iCloud.com and you have your Mail app running on your iPhone (or iPad), then the emails go wherever Apple thinks they go -- most into your Inbox and some randomly to Junk -- and that's all that happens. The only time Rules set in macOS Mail are applied is if your Mac Mail app is the only platform that receives them. That is, your if Mac is powered on and the Mail app is running, but your iOS Mail app is not running, then the rules will be applied. If check your email on your iPhone Mail app while your Mac is asleep or off or the macOS Mail app isn't running, then no rules will be automatically applied, ever.

There seem to be only two workarounds for this:

1. 1. Daily, bulk-select all your unread (or all) emails on your Mac (the Today folder works for me) and go to Message/Apply Rules. They should sort according to your Rules.
   2. Set up an always-on Mac "mail handler." I used an old Mini I have that still runs the current OS. Log into iCloud For best effect, it must automatically restart daily-ish and after power interruption, automatically log in (no password, I believe), and automatically start the Mail app as a Log-in Item. I think it is desirable to connect that Mac directly to your router via Ethernet cable.

At the end of the day, Mail Rules should be synchronized by iCloud and should be applied everywhere. But for now it is per-device only. Unfortunately, there may not be enough people willing to leave Feedback that this will get fixed.