Mojave/Catalina iCloud compatibility?

[Stephen.R]

So far, I haven't upgraded my two work machines (main: 2018 Mac mini; portable/spare: 2018 MBP15) to Catalina, nor my iPhone to iOS 13. Initially I held off when iOS 13 was released because I generally wait till both are available, in case any of the sync/shared features introduce incompatibilities (i.e. I remember iCloud Drive had an 'upgrade' step a few years ago).

Once Catalina was out, there were (a) too many serious issues commented on and (b) I was too busy with work to take a day out to wipe, install & setup two machines on Catalina, plus a phone on iOS13.

So, macOS 10.15.2 and iOS 13.3 were released today, and I'm wondering if its stable enough to try on my "spare" machine, to see how things look. But, I'm still concerned about the iCloud/sync issues.

If something like Safari iCloud tabs stops working, it'll be annoying but not the end of the world (it doesn't work to my iPhone right now, for some reason). But if e.g. iCloud Keychain suddenly breaks, or iCloud Drive is no longer accessible on the older OS's that would be a problem.

So, I'm not expecting "hey chief everything works 100% across the two" - but can anyone comment on, or preferably point me to some actual documentation/information about known, expected "breakages" in iCloud related functionality, between Mojave and Catalina Macs, on the same iCloud account?
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I realise of course I could just not sign in to iCloud on the 'test' machine - but that's gonna make it much harder to setup to accurately test the environment.

 

[Ritsuka]

Safari iCloud tabs will sync only between 10.15 and iOS 13. Reminders can be upgraded to a new format that's only 10.15 and iOS 13 and has got some new features, but it's optional.

Everything else will sync.

 

[Stephen.R]

Safari iCloud tabs will sync only between 10.15 and iOS 13. Reminders can be upgraded to a new format that's only 10.15 and iOS 13 and has got some new features, but it's optional.

Everything else will sync.

Edit: better pic.

 

[petsk]

Safari iCloud tabs will sync only between 10.15 and iOS 13.

This can't be true. My Safari tabs sync fine between iOS13 and 10.14 (mojave).

 

[Stephen.R]

This can't be true. My Safari tabs sync fine between iOS13 and 10.14 (mojave).

Well at the moment I don't even get them syncing between iOS 12 and macOS 10.14, so it appears it's not the most robust of the iCloud sync services.
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And to follow up the original - I'm adding Catalina 10.15.2 to my bootable flash disk to try it out on the MBP15. I already had volumes to install High Sierra, (for a 2011 MBP), and Mojave. Definitely glad I went for the 32GB model - at this rate I should easily get four generations of installer volumes on it.

 

[petsk]

Well at the moment I don't even get them syncing.

For sure, the iCloud services do lagg from time to time. Try rebooting all your devices, if still no luck sign out and then back in on iCloud.

 

[Stephen.R]

For sure, the iCloud services do lagg from time to time. Try rebooting all your devices, if still no luck sign out and then back in on iCloud.

I did the toggle safari sync off/on, reboot/etc - it synced between the two Mojave Macs, and post-catalina install it looks like its syncing between the Mojave Mini and Catalina MBP, so it seems there's something out of whack on the phone.

I'll wipe it too, and update it to ios13.

Once the next thing to try becomes "log out of iCloud and back in" I tend to just put it off until I need to reinstall anyway, because typically the delay for it to sign out, remove everything, and then sign back in, and re-download everything is about the same as just starting from a clean install.