Just to share what I've observered in my home mesh system which consists of following components: -
Fiber Modem -> P7 (main node) -> P7 (slave #1 thru powerline) -> M5 (slave #2 thru wifi) -> M5 (slave #3 thru powerline) -> M5 (slave #4 thru wifi)
My P7s are running on firmware version 1.2 (build 181210 rel. 34913) which does not have new features such as "signal source" nor WebUI, etc.
My M5s are running on Beta firmware version 1.3.0 (build 190529 rel. 36613) which have those new features except WebUI.
Since my main node is P7, as recommended by TP-Link's FAQ on mixed models setup, I loss some new features due to firmware of v1.2 in P7. Since the system is stable, I kind of live with it!
Now, M5 v1.3.1 is released. I wonder if my system can see the new firmware & update accordingly. The answer is 'No"! Again my main node is on P7. The Deco App - "Update Deco" can only report P7 firmware of 1.2. No info on slave M5 at all!
In order to update M5s to v1.3.1, I had to temporarely made one M5 to be the main node. Then the Deco App can see new firmware 1.3.1.
TP-Link has released few new models on Deco. I don't think they have tested issues on different combinations of mixed models...!
End up we, consumers, become their field testers...!