What is causing the packet loss?

A couple things to try with regards to WiFi. These are all separate actions.

-Disconnect from your current WiFi connection, turn WiFi off, power down and then start back up and then enable WiFi and then reconnect.

-Boot into Safe Mode, this will take a bit longer than a normal boot since macOS will do some major "housecleaning". Once you log in, see if the WiFi issue still exists. If it doesn't, shutdown and restart into your normal login.

-In System Preferences->Network, delete the WiFi, reboot and then add WiFi back.

-In System Preferences->Network, if location is set to Automatic, select edit locations and ad a new one and make the WiFi connection again (this will see if you simply have a corrupt network preference file which can sometimes happen).

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

i don't mean to be disrespectful, but if they were in the EtreCheck report, there are still remnants of them distributed throughout your system. and i still see parts of it in the most recent EtreCheck report you've posted.

and, while going over your most recent report for the second time, i see you have a VPN installed. have you done the ping test with the VPN active? if yes, that could be the reason for packet loss. i use a VPN myself to access geo-locked content. but when it's not needed, i always turn it off. when it's active, it very negatively affects my internet connection.

Hi, i have the same issue.

After some testing i had found, that my imac has trouble with my fritzbox 7590 connect over the 5Ghz Wifi Band. If i disabled the 5GHz Band and use only the 2,4GHz the Connection is already fine....

Maybe the Update 11.6 modified the Wifi Driver and caused this trouble....

The same issue is on my macbook pro 16"....

Best regards

You've installed what many users here consider akin to malware, CleanMyMac and Symantec. Neither are necessary as I said in my post above regarding Avast.

Uninstall both according to the developer's instructions. You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For mentioned software you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Name contains macpaw

3 - Name contains symantec

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

devwal wrote:

I removed Avast as suggested but the mini-disconnections / packet loss still occure.

How do I debug this?

you had all this installed.

the damage these apps cause may have already been done. if after completely removing that stuff you still encounter the issue, you unfortunately may be at the point where a complete erase and clean install of macOS will be necessary.

Hello and welcome to Apple Support Communities, devwal!

We understand you've noticed that pages take a while to load on your MacBook. We'd be happy to provide information to help you address this.

Try running a diagnostic to narrow down the issue: Use Wireless Diagnostics on your Mac

Have a great day!

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 user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

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 desshoigned solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

I recommend you uninstall Avast according to the developer's instructions. You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For Avast software you'd do the following search(es): 

1 - Name contains avast

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

Just for accurately - the suggested Wifi Setting for Apple Computers is presented by Apple.

To add to @ Old Toads suggestions

Point # 2 - Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation. The Built-in Security of Big Sur is all that is required.

Any of the above can and will impact the system in ways unseen initially or until things go sideways or down hill

Point # 2 A - Commercial VPNs should only be used if Mandated by Corporate Head Office for working remotely. Otherwise - ones Privacy and Security touted by the VPN is suspect.

It may come down to how new the Router Equipment is and what Encryption process is being used to broadcast the Wifi signal.

Recommended settings for Wi-Fi routers and access points

The only item I see that is questionable is ProtonVPN. If it's required by your bank, school or employer then OK. But it you're using it for privacy reasons it's very questionable.

Here's some food for thought: unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they are useless from a privacy standpoint: Public VPN's are anything but private.