Worried whether external links, maybe repeated in the footer like on this site, could be considered as link scheme by search engines? Well you could make it a
nofollow link manually – or – let WP External Links take care of it automatically. The plugin is highly configurable and does not appear to have any measurable performance hit.
Extract from WordPress.org
Manage all external & internal links on your site. Control icons, nofollow, noopener, ugc (User Generated Content), sponsored and if links open in new window or new tab.https://wordpress.org/plugins/wp-external-links