Safari Default Search Engine

What search engine is in use?

You may  have adware/malware installed. Try downloading this program which was written by Thomas R, a long time poster. The program will search for malware/adware. The program will do the work for you which makes it easy. It may be necessary to run more than one scan. After running the scans, restart the computer.

Malwarebytes Anti-Malware for Mac      10.10 and later

Malwarebytes uninstall

Download and run Malwarebytes. It may be necessary to run more than one scan. After running the scans, restart the computer.

If necessary, follow the manual instructions.  Do not download any other programs that are listed in the articles.   Malwarebytes uninstall

See if the below helps. I would scroll down to the below or you might fall asleep.

Step 1. Eliminate Yahoo Redirect from Windows

Step 2. Delete Yahoo Redirect from Mac OS X

Step 3. Uninstall Yahoo Redirect from Internet Explorer

Step 4. Remove Yahoo Redirect from Microsoft Edge

Step 5. Erase Yahoo Redirect from Mozilla Firefox

Step 6. Get rid of Yahoo Redirect from Google Chrome

Step 7. Eliminate Yahoo Redirect from Safari

https://www.2-spyware.com/remove-yahoo-redirect-virus.html