BENQ 2710QC ETHERNET STOP WORKING with VENTURA

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

Also, unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they aprovide false secutiry from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Former Malware Distributor Kape Technologies Now Owns ExpressVPN, CyberGhost, Private Internet Access, Zenmate, and a Collection of VPN “Review” Websites. 

That being said uninstall PACE according to the developer's instructions. Also consider uninstalling your VPN app also unless it's needed for your banking, employment of school.

That because many many users and Apple now to lock down their Macs and not allow this. This is called System Security that prevents this So do this at your own risk!

Boot into Use macOS Recovery on a Mac with Apple silicon - Apple Support and follow the steps to turn of this security setting to use Macs like you were able to in the past!

Does the usb-c dock in your BenQ monitor require any driver installation or is it just plug and play?

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

Major Issues:

Anything that appears on this list needs immediate attention.

Automatic updates disabled - Automatic updates are disabled. This computer is at risk of malware infection.

Security updates disabled - Security updates are disabled. This computer is at risk of malware infection.

Kernel panics - This system has experienced kernel panics. This could be a sign of hardware failure.

Apple security disabled - Apple security software is disabled. This computer is at risk of malware infection.

Having the built-in system security is never a good idea. Probably not what is causing the present issue, but an unnecessary risk.

You don't have to turn on automatic OS updates (I much prefer to do them manually, after hearing the first user reactions and having made sure to have an up to date backup).

But security updates should be installed as soon as they come. And SIP should not be left turned off. In the rare occasions where turning it off may be needed, it should be turned back on as soon as possible.

I would try uninstalling surfshark and see if it helps.

Also, as a test: does the same loss of ethernet occur if you do the same speed test in Safe Mode?

There were two kernel panics two days ago. These are fatal crashes where the whole system goes down, requiring a restart, and could be caused by hardware or a software extension. Did this happen in connection with a situation like the one described in this thread?