Relative links in Gutenberg

It doesn’t have anything to do with Gutenberg. It’s just the way WordPress stores links in the main content. Anytime you add a link in the WP editor, it automatically puts in the absolute path. ACF and other forms of custom postmeta instead store the post ID, so whenever its slug/permalink changes they are automatically updated.

When you push content from your local site, just use a database migration plugin, which will handle all the URL changes.