Hi, on the Options page, "Home" panel:

Is there any indication that an extension has taken over or is controlling your home page?

Can you resolve the issue by either changing the Custom URLs list or switching to the built-in Firefox Home page or a blank page? (How to set the home page)

Oh, I should have checked the data you shared about your add-ons: this one looks suspicious:

Sponsored Search by QuickForms

If it also interferes with using the Add-ons page, it's best to restart in Firefox's Safe/Troubleshoot Mode. In that mode, Firefox temporarily deactivates extensions.

If Firefox is running:

You can restart Firefox in Safe/Troubleshoot Mode using either:

• "3-bar" menu button > Help > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled)
• (menu bar) Help menu > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled)

and OK the restart. A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button).

If Firefox is not running:

Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button).

Note: Don't use the Refresh without first reviewing this article to understand what will be deleted: Refresh Firefox - reset add-ons and settings.

Can you flush it?

You can find the install location of a specific extension in the extensions.json file in the profile folder. You can open the extensions.json file in a Firefox tab and search for this extension. The path field lists its install location.

• https://developer.mozilla.org/en-US/docs/Tools/JSON_viewer

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

You can find the install location of a specific extension in the extensions.json file in the profile folder. You can open the extensions.json file in a Firefox tab and search for this extension. The path field lists its install location.

• https://developer.mozilla.org/en-US/docs/Tools/JSON_viewer

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

This did the trick for me.