How do I get to the about:config page? It says Connection is not secure. There is no popup which asks "if I am sure".

What I tried already:

• Disabled all extensions
• Disabled all system wide tracker and ad blockers
• Turned off HTTPS only mode
• Turned off Enhanced Tracking Protection

Didnt know how to enter Safe mode in Firefox for Android. So couldn't try that.

• Wiped cache and all app settings using Android Settings:App menu.
• Uninstalled Firefox.
• Reboot Device.
• Reinstalled Firefox.
• about:config does same thing; no change.

This happens on both my Android Tablet and my Android Phone, both Samsung. Any ideas?