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: https://support.apple.com/guide/mac-help/configuration-profiles-standardize-settings-mh35561/mac
2. Remove unknown extensions: Safari > Preferences > Extensions
https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac
3. 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.
4. Reset search engine: https://support.apple.com/guide/safari/customize-your-search-ibrwe75c2a3c/mac
5. Reset Homepage. https://support.apple.com/guide/safari/set-your-homepage-ibrw1020/mac
