Go to Settings -> Search -> Search Shortcuts (at the bottom), and view the search engines that are checked. Remove any search engines you don't want to use by clicking on its bar and then the Remove button. Now make a search. Is the issue persisting?

If so, open Firefox in Troubleshoot Mode (Hamburger menu -> Help -> Troubleshoot Mode...). Then, try to search again. If the issue is fixed, it is likely one of your extensions that is causing this issue. Open Firefox in Standard Mode, disable extensions one at a time, making a search after every change. If disabling an extension fixes the issue, remove that extension.

Loaned my laptop to someone (ex wife), got it back and looks like search owl has hijacked firefox. Tried the above suggestions, still happens. What will happen if I uninstall and re-install? This is what y'all mean by a clean install, right? OP says Malwarebytes and TotalAV didn't find anything. Possibly McAfee or Avast might?

If opening Firefox in Troubleshoot Mode does not solve the issue, a Firefox extension is not the cause.

Does the search hijacker persist if you try searching with other browsers on that same device?

If using Windows: What are the results of running a Windows Defender scan? In your Windows settings, you should be able to access a comprehensive list of apps on the device. Do you see any suspicious apps? If so, click on the three dots for that respective app and uninstall it.