The log snippet you have shared largely shows the process of getting associated successfully. I note the first 3 lines log a disconnection event and a reason code....
Reason code 3 is 'Device is now unmanaged'. Now, sometimes that can arise because another network management framework is being used concurrently, and this can lead to obvious conflicts. However, in your case I'm wondering if this is due to an issue with the wireless device itself. Did you try the suggested config (post #6) as of yet?

I have not yet tried the config file in post #6 yet because I thought this might isolate the problem. I will do so now. BTW this laptop is cable connected to the modem/router (Cisco DPC3825).

??? Your log is about wireless connectivity. You need to clarify further here.

???

My original post said this, which you acknowledged in a subsequent reply. I have never referenced anything but a cabled connection to the router.

You asked me to run the log and I assumed it would produce what you wanted to look at with respect to a hardwired router connection.

It's because you described your router as a wifi router and your phone connected vie wifi as well I guess. Your log shows that your wireless is connecting. Disable that to start with, so that we can concentrate solely on your wired ethernet connection.

Your USB ethernet device is reported as
It's likely that USB power management is the issue here. Not all device drivers support it. Here's a thread with an answer that shows how to inhibit it...
https://askubuntu.com/questions/1140...n-ubuntu-18-04

In particular, try doing the following
then see if the USB ethernet device behaves better for you.

1 members found this post helpful.

OK thanks. I have run that script and we will see what happens today. It does seem possible that this is a USB power management issue. My laptop does not have an input jack for a standard coax cable from the router so I use an adapter to convert to a USB port. That adapter usually has a small blue led lit to show it is functioning. Lately that led has not been lit or has been intermittent. I'll report back after seeing if this works.

Yes, this is the most likely cause. Anyway, fingers crossed.
Usually an ethernet port (designed to take ethernet cables with RJ45 connectors).

That appears to have solved the problem. No internet drops for a day now Which begs the question what caused this in the first place? I have had this laptop running Manjaro-Budgie for about 2 years without issue until about 10 days ago. I haven't installed anything new recently, except updates that Manjaro pushes out, so it would seem that something in one of those triggered the problem.

About the same time, I did discover one bug which emanated from Ubuntu in the Previews Control function of the Budgie DE. It was hogging about 65% of CPU and causing Xorg to take about 70% of CPU, to the point that my CPU was heating up to around 75-80C and the fan was running constantly. I disabled Previews (which I don't use anyway) and that problem resolved. Connected??

That is good news.
Possibly power-management changes within the kernel? I'm not sure. I don't own such a USB NIC device, but what I do know is that some of the drivers cannot cope with USB power management, and therefore it can be disabled on a per-device basis, or completely (as you have now done). Some laptop users install TLP laptop power management. It's very configurable and available for most distros...
https://linrunner.de/tlp/
I'll leave that as en exercise for you to investigate further.

I will look into TLP. Again, thank you for all your help. It has been much appreciated.