There is no option to hide the tagline or site description in the Twenty Twenty theme. You can follow the steps below to hide the tagline.
Step 1: Go to Customize under Appearance
Step 2: Go to the Additional CSS section & add the following CSS code. After adding the code, you will have to hit the publish button, so that the changes have been saved.
.site-description{display:none;}
Tip: You can also hide the tagline by making the Tagline field empty. You can find it under Settings >> General.
How to hide Tagline for
Twenty Twenty-One theme:
Step 1: Go to Customize under Appearance
Step 2: Navigate to Site Identity
Step 3: Uncheck the option where it says, “Display Site Title & Tagline”
If you are not able to hide the tagline following the above methods, do let me know in the comment section below. I would like to help you out.