@Rogerbee 

It would appear that I spoke too soon!

Even with that driver installed, I was watching a video on YouTube and the adapter spontaneously reset itself at least 4 times! I had 3 other browser tabs open at the time and closing one of them seemed to stop the resets. I have NEVER had this happen before. I've watched whole live streams on YouTube with several other browser windows open and have never had a single issue.

Just now, it completely shut down!! I had to use the troubleshooter in Windows to get it going again. This just isn't good enough!

I may have to return this and get something else!

  @Rogerbee 

Ok, here's a thing. I watched a YouTube video where someone had been having the same issue, but with a Netgear A7000. It has a Realtek chipset. They said that the driver installed and started a service called RunSwUSB. Disabling that is supposed to solve the issue.

My T9UH is now boxed up awaiting return, but, my old Asus AC-56 also has a Realtek chipset. Up until I did a feature update to 21H2, I'd been using a 2016 driver and this had been rock solid. I'm starting to think that this driver didn't have the service packaged with it. The service was still there from the T9UH drivers. I went back to the 2016 AC-56 driver and this had issues until I disabled the service. Now, it  is back to rock solid.

I can't guarantee that installing an older driver and disabling RunSwUSB will solve things with the T9UH, but, heck, it can't hurt to try, can it!?

Good luck!

CHEERS!

  @Solla-topee 

Well for the AC-56 it did. Can't vouch for the T9UH.

One other thing, because of where the router is and where my PC is, I have to use an extension cable to connect the adapter to my PC. It did occur to me that this might contribute to the issue. I've ordered a new cable and will see how I get on. It's only been in the past week or so that I've been noticing any issues. That was why I thought it was the adapter getting old as ones I'd had previously started expiring after years of constant use.

I'll see what happens, I'm definitely holding off getting anything more potent than the AC-56 for now

CHEERS!

  @Rogerbee 

One other very important thing. Whatever is causing these issues, I firmly believe it is driver related, it is NOT power related! I had device manager open when one of the outages took place. The device manager screen refreshed when it happened. This would suggest a driver problem.

A lot of 'remedies' advise you to change power settings, don't! Altering one of these caused a serious shutdown issue. When attempting shutdown, the PC was unable to turn off the wireless adapter and it would not shut down. The only way to do so was to reset, let the PC restart and then it would shut down. This has to be power related. I went back to every 'allow the computer to turn off this device to save power' setting and re-enabled it. I'm pretty certain that the PC needs this setting on in order to be able to turn off the device at all. Once I had changed these settings, the PC shut down normally.

The adapter driver still refreshes twice on start up, and I still have no idea why, but, as far as I know, the PC will at least be able to turn it off when it shuts down.

I hope you find this helpful

CHEERS!