You can change the font directly in the app.
1. Open Covet.pics and go to the Customize Gallery screen
2. Scroll down the left settings menu to Style Settings
3. Click the Font dropdown box and select a font
4. Save Changes
If you don't want to use Google Fonts that app provides, you can use your own custom font by changing Font property in Customize Gallery screen and setting a CSS variable. Here is how to set it up:
Step 1. - Change font to "None" in Embed settings
Step 2. - Change the CSS variable
When font is set to None, gallery will inherit whatever font you have on defined on your site as a default font. You can further customize it by setting CSS variable "--covet-pics-font-family"