I had been running a pair of wifi5 devices on 22.03.7 in router-dump AP tandem, with the latter configured according to the official wiki for bridged AP.
Now that I'm making the jump to a pair of Redmi AX6 (RA69) wifi6 devices, I figure I might as well go with the latest stable release which is 25.12.4.
Very first order of business after getting 25.12.4 sysupgrade image flashed was changing the IP addr scheme to my pref. of using the 10.0.0.0/8 space. However, on the new dumb AP, it kept failing to apply and always trying to revert to the defaults after 90 seconds (the latter part is a fail-safe feature obviously). The one time I rebooted the dumb AP before it could revert, I couldn't get on it in any way anymore (requiring a soft reset to defaults), even though the dumb AP functioned as it should on the network, and the 10.x.x.x static IP addr could be seen in the main router's ARP table. But for a dumb AP, there aren't many knobs to touch at all. Luckily I quickly got suspicious of the Global network options settings, partly from past experience of configuring IPv6 for the router-dumb AP tandem, partly on a hint from the caveat under the Packet Steering option (disabled, enabled, enabled (all CPUs)) that having it on might help or hinder network speed, as well as thirdly a faint recollection of reading somewhere (here or elsewhere online) of packet steering causing trouble. Lo and behold, disabling Packet Steering did the trick, and after further experimentation, enabling Packet Steering (all CPUs) works also, for allowing re-addressing the 'lan' interface without consequently blocking external access to the dumb AP (I scanned with Nmap, which reported all 1000 ports closed, if Packet Steering was left on, but not for "all CPUs".)
The question is, is this issue peculiar to 25.12.4, or just Redmi AX6 running 25.12.4? I looked on my two 22.03.7 devices (MTK762x and ATH7xxx), both have Packet Steering disabled. I don't recall disabling/touching it, ever. Nor do I find Packet Steering mentioned on the bridged AP part of the official wiki that I followed. Is it possible to make the Packet Steering default of 25.12.4 "safer" [for IP re-addressing], at least for Redmi AX6 if it's the only model affected?