As I normally do applied settings specific to customer location, and tested everything then attempted to upgrade from 7.6 arm64 to latest 7.9 arm64 and wireless interfaces are gone. Tried downgrading back to 7.6, factory defaulting router, restored original backup but nothing and as shown below /interface wifiwave2 no longer applicable, retrieved command from original backup on how it defined wireless interfaces. Just opened case via Support Portal (SUP-115150), posting here as a warning for everyone hold off attempting to update as it looks like a bug exist.

may/02/2023 16:30:32 system,error,critical error while running customized default
configuration script: interrupted
> /interface wifiwave2
bad command name wifiwave2 (line 1 column 12)

Sounds like you upgraded manually and didn't also include the wifiwave2 package (both main package wifiwave2 package are required when doing the update manually). Using the upgrade button from winbox packages should download all packages.

Using the upgrade button from winbox packages should download all packages.

To reinforce this statement:
On my AX devices (I have 3) I have never seen a fail using Upgrade with button (or CLI, it's the same).
I DO have seen this fail when doing manual up/downgrade or netinstall (and forgetting about the wifiwave2 package in all cases).
I even seem to recall a factory reset on AX3 and there was no wifiwave2 package anymore. Just add it and all is well.

You are both correct as support came back with the same answer, wifiwave2 is part of the extra packages when upgrading/downgrading via custom scripts, manual upgrade or downgrade paths and needs to be added just like the base routeros npk file, so now off to modify the custom upgrade scripts to watch for it.