The conclusion of that thread was that there is no harm in having a desktop and mobile H1 – Google will not penalize you for it, and it’s better for accessibility.
However, you can tell GP not to make the titles an H1 like this:
add_filter( 'generate_site_title_output', function() {
return sprintf(
'<p class="main-title" itemprop="headline">
<a href="%1$s" rel="home">
%2$s
</a>
</p>',
esc_url( apply_filters( 'generate_site_title_href', home_url( '/' ) ) ),
get_bloginfo( 'name' )
);
} );
Then you can use a Hook Element (https://docs.generatepress.com/article/hooks-element-overview/) to add an H1 to your homepage.
Let us know if you need more info ๐