Thanks to leyabe on Reddit:

Settings | About | Firefox.

Tap the logo multiple times until the developers settings are enabled.

Go to Settings | Secret Settings

There, toggle off : Toolbar Customization, Redesigned Toolbar, Composable Toolbar, and at the bottom, Tab Manager Enhancements..

Kill and restart Firefox.

Thank you for your help. I also found this to do after as well after your suggestion.

How to revert to the older design?

       Tap on the Settings button, which comes up after you click on the three-dot menu in the corner.
       Tap on ‘Data Collection’ from the Settings menu.
       You’ll find an option called ‘Studies’ from here.
       Remove the option that says ‘Android Brand Refresh’ or ‘Android Redesign.’
       Force stop the app from settings and clear cache. Restart the app. You should get the old design back

Hi folks,

Just a note that opting out of the Study is just a temporary workaround, and you'll eventually get the new design when Firefox hit version 149.

To share feedback about the new Firefox for Android design, you may want to post in our feedback platform, Mozilla Connect instead.