1. Check for adware.
Run the latest release of Malwarebytes for Mac to remove malware/adware, if installed on your Mac.
For instructions: Install Malwarebytes for Mac v4 Uninstall Malwarebytes for Mac
Click the “Scan Now” 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.
2. Reset search engine: https://support.apple.com/guide/safari/customize-your-search-ibrwe75c2a3c/mac
3. Reset Homepage. https://support.apple.com/guide/safari/set-your-homepage-ibrw1020/mac
Adobe Flash
Note:
Apple Safari version 14, released for macOS in September 2020, will no longer load Adobe Flash Player
or play Flash content. Please visit Apple’s Safari support for more information.
https://helpx.adobe.com/flash-player/kb/enabling-flash-player-safari.ug.html