My iMac was only able to connect to WiFi one day a week for about 6 hours

Doing a quick review of this EtreCheck report, the #1 thing I strongly suggest that you do is completely remove CleanMyMac and any additional "cleaner" apps from your Mac. We get numerous posts here from folks asking us to help troubleshoot their Mac issues only to find out that they have these cleaners installed. In almost all cases, completely removing them fixes their issues.

macOS is extremely secure. Whether or not, you want to add "useless" security apps beyond that, of course, is your decision to make. FWIW, I only have Malwarebytes for Mac installed on my Macs ... and I have been doing so for years. However, in all honesty, it has NEVER found any malware on any of them.

As far as time-limited Internet access, I have already added my "2 cents" on this topic on your other post. There is nothing in the report, outside of having "cleaner" apps, that could potentially be causing this issue.

One thing I do suggest, it that you take a look at your Mac's hosts file. It is located in the /etc folder on your Mac. If it contains additional links, then it could have been compromised. The following articles should provide you with some additional details on what I am referring to here:

• Fixing a hacked /etc/hosts file - Apple Community
• https://www.imore.com/how-edit-your-macs-hosts-file-and-why-you-would-want

These types of programs are not recommended and should be removed with any provided uninstaller:

• Cleaners
• Optimizers
• AntiVirus
• CleanMyMac

Based on your EtreCheck report these files could cause problems:

• AdBlockVPNMacOSProvider
• AdBlock app
• ProtonVPN WireGuard
• ProtonVPN OpenVPN
• com.adguard.mac.adguard.pac.plist - in /Library/LaunchDaemons Folder
• com.adguard.mac.adguard.tun-helper.plist - in /Library/LaunchDaemons Folder
• AdGuard Software folder - at /Library/Application Support
• com.piriform.ccleaner.CCleanerAgent.plist - in /Library/LaunchDaemons Folder
• com.piriform.ccleaner.engine.xpc.plist - in /Library/LaunchDaemons Folder
• com.piriform.ccleaner.services.submit.plist - in /Library/LaunchDaemons Folder
• com.piriform.ccleaner.uninstall.plist - in /Library/LaunchDaemons Folder
• com.piriform.ccleaner.services.xpc.plist - in /Library/LaunchDaemons Folder
• com.piriform.ccleaner.update.xpc.plist - in /Library/LaunchDaemons Folder
• net.protected.macos.AVHelper.plist - in /Library/LaunchDaemons Folder
• com.piriform.ccleaner.plist - in /Library/LaunchAgents
• com.piriform.ccleaner.update.plist - in /Library/LaunchAgents
• com.macpaw.CleanMyMac4.Updater.plist - in ~/Library/LaunchAgents

As stated previously, you will want to use any provided uninstaller for the programs and move the Applications to the trash. Some of the files listed above are bundled into the Application file and will may not show at that physical location provided, but will be removed when the application is deleted. To further investigate what could be going wrong with your system, you must remove the categories of files that are known to cause problems first. After that post an updated EtreCheck report to make sure no files have been left behind.

You also have various VPN apps installed which do ZERO to help your Mac, please uninstall each. To ensure the Cleaning Apps and VPN's are gone download FindAnyFile and use it to search for anything with the words:

• CleanMyMac
• MacPaw
• ProtonVPN
• OpenVPN
• WireGuard
• piriform.ccleaner
• AVHelper

and ensure those files are Trashed and the Trash has been emptied. Going forward NEVER install the following types of apps:

·      Antivirus Apps

·      Cleaning Apps

·      Security Apps

·      VPN Apps

·      Maintenance Apps

I wholeheartedly agree with Tsserax on CleanMyMac. 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.  

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, public VPNs provide false security from a privacy standpoint.  Read these two articles: Public VPN's are anything but private, Former Malware Distributor Kape Technologies Now Owns a Number of Public VPNs and a Collection of VPN “Review” Websites and Security Risks: The Dangers of Using Free VPNs (eccu.edu)

Uninstall CleanMyMac 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 CMM software you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Name contains macpaw

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.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.