how to get rid of search marquis without buying a cleaner?

Getting rid of "Search Marquis" is easy and you don't need to install anything.

To ascertain the cause so that you can eliminate it, start by inspecting the contents of the following folder:

~/Library/LaunchAgents

To open that folder, copy the entire line above and paste it in the Finder's Go menu > Go to Folder... field. Make it look like this:

... and click the Go button.

A Finder window will open. Make sure all its file names are readable by selecting View > as List or other selection that shows that folder's complete contents. Then, take a screenshot of that Finder window.

• To learn how to capture a screenshot please read the Appendix in the following User Tip: Writing an effective Apple Support Communities question. It also includes instructions for posting a screenshot in a reply to this Discussion, so keep that Safari window open for now.

Often, there is nothing in that Launch Agents folder so don't be surprised to find it empty.

In the same manner as the above, navigate to this next folder:

/Library/LaunchDaemons

The Finder's Go menu > Go to Folder... field should look like this:

... and click the Go button once again.

Once again ensure all its files and their names are readable and capture a screenshot.

Then, repeat that exercise with the following folder:

/Library/LaunchAgents

Notice its pathname is different than the other two. The Finder's Go menu > Go to Folder... field should look like this:

In the end, you will have captured the contents of the following three separate folders:

~/Library/LaunchAgents

/Library/LaunchDaemons

/Library/LaunchAgents

All three will be saved to your Mac's Desktop with names "Screen Shot... " followed by the date and time they were captured. Please be sure to include or otherwise indicate the name of the folder that corresponds to each screenshot, so that you and I can keep track of which ones they are.

Post the entire contents of all three windows, one at a time, using the "picture" icon that appears below your reply text:

Malwarebytes for Mac is free for Mac users.

Go step by step and test.

   1. Remove unknown profiles if present.

      System Preferences > Profiles

      Open System Preferences,  select “General and click  the “Profiles” icon ( a checkmark on a gear) .

      When Profiles pane opens, select the unknown profile and click the minus button at the bottom.

      Section: Remove a configuration profile from your Mac

      Profiles: Use configuration profiles to standardize settings on Mac computers - Apple Support

  2. Remove unknown extensions:  Safari > Preferences > Extensions

      Get extensions to customize Safari on Mac - Apple Support

      Change Extensions preferences in Safari on Mac - Apple Support

   3. Check for adware.

       Run the latest release of Malwarebytes for Mac to remove malware/adware, if installed on your Mac.

       For instructions: For instructions:

          Install Malwarebytes for Mac v4                                                

          https://support.malwarebytes.com/hc/en-us/articles/360039025233-Uninstall-Malwarebytes-for-Mac

       Click the “FREE DOWNLOAD” button.

       Click the “Scan” button. Once done, quit Malwarebytes for Mac.

       Restart the computer and relaunch Safari holding the shift key down.

       Scan for Malware again.

       Additional steps  if necessary.

  4. Reset search engine:    Customize searching in Safari on Mac - Apple Support

  5. Reset  Homepage.   Change your homepage in Safari on Mac - Apple Support