Are there any backdoor logins on the stock EU (non-Malaysian) firmware? I didn't see a setup page for TR-069. I might try to get the rest of the 5G wifi channels working following the guide in this thread but thats for later.

Is the router patched against krack with stock Msian/EU firmware? I saw post earlier in the thread which said that it wasn't.

Not on the current firmware.
The really old 2016 rom version might have the setting for upload/dl limits for guest network but its buggy.

The current UK firmware is abit odd, I came across a problem where the 2.4Ghz wifi channel setting may be missing channels 12-13 in the drop down list. Had to do a hard reset to get those back.

Or the 5G wifi channel drop down menu may have channels 1xx which are normally missing. Unfortunately those don't work, I tried and it maps to channels in the 36-64 range instead.

The problem can happen after several factory resets as well. The router is still showing the upper 5G channels in the drop down list (but they don't actually work as I explained above).

Definitely not, as I said, the rom is abit iffy, it doesn't happen often and it might only show up during the first wifi setup.