Implement hreflang with multi sites I currently have multi site config. One site have 2 locales.
My configuration like so:

'example.com' =&gt; array(
    'siteUrl' =&gt; array(
        'us_en' =&gt; 'https://www.example.com/',
        'br_sp' =&gt; 'https://www.example.com/sp'
    ),
'example.uk' =&gt; array(
    'siteUrl' =&gt; array(
        'uk_en' =&gt; 'https://www.example.uk/',
    ).


I'm using SEOmatic plugin.
Hreflang requires all site have to list on the head of page.
However, SEO list 2 locales which are us_en and br_sp on a site only.
How can I do it?
You're going to want to ensure that all of the sites that are a translation of each other are in the same site group, as detailed here: SEOmatic Multi-Site Language/Locale Support