You need only to type a few characters. Ensure the text is in the font you desire as the default for Google Docs. (We use Rubik.)
Highlight the text by dragging your cursor across it.
With the text still highlighted:
- Go to Format.
- Select Paragraph Styles.
- Select Normal Text.
- Click Update 'Normal text' to match.
In order for your new font selection to remain the default each time you open a new Google Doc, you need to save it.
- Go to Paragraph styles.
- Select Options.
- Choose Save as my default style.
Now, your default font will be your new font whenever you start a new Google Doc. You can also change the default fonts the same way for various headings, as well.