Hi there!

This snippet should disable text decoration throughout the store:

/* Remove text-decoration */

a {
    text-decoration: none !important;
}

Please navigate to Dashboard > Appearance > Customize > Additional CSS, add the above snippet and then click on Publish button to save changes.

Hi there!

Question, when you say “text-decoration” does this mean remove just the underline from links in post content, footer, and breadcrumbs? Or will it remove all formatting?

The snippet above would remove formatting on all the links in your site.

If you only want this applied to post-content, footer, and breadcrumbs, you can use the following snippet instead:

.woocommerce-breadcrumb a, .site-footer a, .entry-content a {
	text-decoration: none !important;
}