This network is operating on Wi-Fi channels in use by several other nearby networks

I did in the last 1-2 weeks get an error on my WI FI portion of my home LAN. A number of my WI FI devices in my home suddenly failed to connect while ethernet devices connected fine.

My 2021 iPad Mini running iOS 15.71 also failed to Connect via WI FI but gave this error statement:
“Unable to join the network [name]”, on account of “This network is operating on Wi-Fi channels in use by several other nearby networks.”

I had never seen this type of error or error statement on my Macs, MacBookPro or iPad or home LAN before.

I use an older ASUS router RT-AC68U which still funcitons fine. On checking with WIFI EXPLORER about 6 nearby neighbors were using CHANNEL 1 under 2.4GHz WI FI and my ASUS router was set to use this same channel. I switched settings in the ASUS router to CHANNEL 6 and all problems have since disappeared.

Is this an iOS bug? My iPad Mini is currently iOS 15.7.2 and I am not certain when that iOS update occurred BEFORE or AFTER this WI FI error.

No, not an iOS bug.

Co-channel interference by overlapping signals of equal or nearly equal received signal strength (RSSI) often results in difficulty for the receiver to lock to the desired signal. This problems occurs at the WiFi hardware level, not the OS level. Your solution of moving the WiFi channel on your router to a non-busy channel was the proper solution and also shows the value of tools like WiFi Explorer for understanding your WiFi environment.

Side notes: There are only three non-overlapping channels in US 2.4GHz WiFi channels – 1, 6, and 11. Many newer routers check channel usage at startup and pick what seems the channel with least interference possibilities.