Did some testing over the weekend with ... Messages.
IPP 11 2020 and 12 ProMax both on 14.4.b1
Both have the same Messages setup. Using Phone number (12PM) and iCloud (12PM / IPP 11) and forwarding from 12PM to IPP 11
Tested Messages, SMS, MMS, and Forwarding 12PM > IPP 11.
Messages sent from 12PM and IPP11 and SE 2020
Messages sent from Non iOS used: Razer, Galaxy S8, Note 10.
Tested Notifications 12PM Badge and Lockscreen with Apple Nike Watch 4 GPS along with Badge and Lockscreen IPP 11.
1. All Messages sent from SE were received by 12PM and IPP11. Badges matched. Lockscreen Notifications matched. Notifications showed on AW4 but no sound played.
2. All SMS sent from Razer, S8 and N10 were received by 12PM. Badges matched. Lockscreen Notifications matched. All SMS forwarded from 12PM to IPP11 failed. Notifications on AW4 all failed to show.
3. All MMS sent from Razer, S8 and N10 were received by 12PM. Badges matched. Lockscreen Notifications did not match - less than 50% had a corresponding Notification. All MMS forwarded from 12PM to IPP11 failed. Notifications on AW4 all failed to show.
4. Messages sent via 12PM (phone number) to SE were properly received. Messages sent via iCloud (12PM and IPP11) to SE were properly received.
5. Messages sent SMS/MMS to SE were all properly received. Messages sent SMS/MMS to Android devices took up to 10 seconds to send for SMS and up to 30 seconds for MMS. Had 2 instances where the MMS failed. All SMS/MMS without a failure notifications were received by the Android devices.
6. Messages marked as READ on either the IPP11 or 12PM frequently failed to change status on the other device. Also ran into where the Message showed up on the IPP11 in an already read status without ever being opened.
All issues reported via Feedback.
Note: the Notification issues with Messages looks to be working better. With iMessage set, SMS/MMS to Android is still an issue. Same with forwarding SMS/MMS.