Multiple H1

GeneratePress sets the site header as H1 when the front page is set as the blog page.

You may modify this behavior through a filter. Can you try adding this PHP snippet:

add_filter( 'generate_site_title_output', function( $output ) {
	return sprintf(
				'<%1$s class="main-title"%4$s>
					<a href="%2$s" rel="home">
						%3$s
					</a>
				</%1$s>',
				'p',
				esc_url( apply_filters( 'generate_site_title_href', home_url( '/' ) ) ),
				get_bloginfo( 'name' ),
				'microdata' === generate_get_schema_type() ? ' itemprop="headline"' : ''
			);
});

Adding PHP reference: https://docs.generatepress.com/article/adding-php/#code-snippets

Kindly let us know how it goes.

That's it!

Nice answer Fernando.

You’re welcome David! Sorry again for the misunderstanding! Hope you have a nice day!

Well, that was nice. You too!