I've been battling the "printer disconnects from Wi-Fi problem" for 6 months, maybe more. I've tried so many things and I'm determined to not give up. I see this as a widespread problem so I thought I'd share what I've learned with the world. So relax, get a cup of coffee, and read on.
I have a windows 11 pro OS and a TP Link AX 3000 4-stream Wi-Fi 6 router and a brother Wi-Fi (only) printer. My printer is in a closet 40 ft away from my router which is in another closet. My Wi-Fi is configured to use both 2.4 GHz and 5 GHz channels (Smart Connect) and I'm convinced that that actually seems to work fine. Many devices only work on the lower band, but that seems to get negotiated without my intervention other than I believe there is a setup in the router configuration to enable that feature. I was pretty frustrated because I do have an increasingly large number of devices (clients) using Wi-Fi in my house: 2 pc's, 2 android cell phones, 3 Sonos speakers, 3 WAC fans, one TV, one water softener, one humidistat in my crawl space, one Honeywell HVAC thermostat, and of course my printer.
To cut to the chase, my biggest problem, by far was the Honeywell thermostat. It does not play well with others. It interferes with the Sonos, the printer, and even the TV! The TV would not respond to remote controller commands as quickly as it did before adding the thermostat to the LAN. That was strange and troubling. I wrestled to get the Sonos working for weeks. But the problem was that Honeywell Home thermostat. The thermostat worked fine, it would control the temperature in the house remotely, but for some unknown reason, it interfered with Sonos speakers, Sony TV and the Brother Wi-Fi printer. Once I disabled the Honeywell thermostat Wi-Fi and got all other clients back on line, my life improved. My home Wi-Fi stability was ''mostly'' restored. The thermostat does work, only without WIFI. I don't know what the specific problem is but it is not a priority in my life to solve at this time.
There is another slightly less annoying problem causing my printer to go offline. I believe it has to do with auto updates on the printer and the router. It seems that whenever there's an update, the printer goes offline and cannot be restored without a hard (power) reset on the router. These auto updates can be disabled, and that is what I have done (both auto firmware updates for the printer and the router). I believe it's best to manage these updates somewhat infrequently, by me, and not randomly by the manufacturer and not frequently.
So, keep in mind you may also have multiple problems hindering smooth Wi-Fi operation in your home. Please keep sharing your Wi-Fi troubleshooting wisdom. I believe Wi-fi is an ever evolving technology and new issues probably lie ahead. Good luck.
Cheers!