Okay, but that is not quite an answer I was looking for. I was wondering how to inject this form or a simple checkbox somewhere, so the users can easily subscribe to the newsletter.
For an example in Shopware 5 in home page footer there is a small text form for a subscription (like a screenshot which I have sent in the previous comment).
Also in Shopware 5 in settings for checkout, you can include newsletter subscription checkbox in the checkout process. Is this option not available in Shopware 6?