u/AltTabMafia

1. Click on the three bars on the right-hand side.
2. Click 'Settings'.
3. On the left-handed side, click 'Search'.
4. Scroll down to Search Shortcuts
5. Click 'add', a new screen will pop up.
6. Name it 'Startpage'
7. In the URL, paste in: https://startpage.com/sp/search?query=%s
8. Leave the keyword space empty, click 'Add Engine'
9. Scroll back up, set Startpage as your default search engine.

Some additional optional moves are removing the new search engines or removing Waterfox and going to Librewolf.

Hope this helps!