There is a functionality to show popup dialog with newsletter subscribe form. The popup has its own setting in redaction (available only to Admin role). The Sidebar widget is also available as same as top menu subscribe link.
There are 4 parameters which control when and how often is popup shown on page to specific user (specific relation - as we do not track users across their devices / web browsers).
The settings is available in Settings > MailGuide > Settings tab
To show popup both condition must be true - 2) and 3) and there must be expired previous occurence of popup or not set.
To test this functionality - Use Browser inspector and Open Local storage There are 3 entries representing 2,3,4 points from the above numbered list.
4/2023
Added newsletter link override in Story header section. You can use it for adding link to custom page or even external newsletter page. It does not require to have Newsletter enabled for specific language.