You dont appear to be able to search modern pages from SharePoint Online - unless they're marked as news.
We've moved what was our existing old style SharePoint wiki library, into a modern page library in a communications site, and while you can find these pages when searching from SharePoint in the web browser - they don't appear when using the Search box inside the SharePoint for Mobile.
I expect the SharePoint for Mobile app - has some logic, that includes the display of 'wiki pages' and modern pages marked as news pages - but I cant see how we can ensure that our modern pages - which are important knowledge articles get returned for phone users.
