No problems, you just need to know an SQL query to load the report data.

... some single articles (always from slave sites) and there will be a menu with shared items. Clicking on a shared category present in the menu will load all the articles that have that category of all the slave sites and clicking on the entry of a single blogger, for example, all the latest articles ...

... block on term page with this news page. Please note that once installed, all current usage pages are emptied and will be auto-populated on page load. Hence, all usage data and mentions will be re-created soon. Full change log: ⋅ Feature: canonical URL tags for category and term pages. ...

... All sites are separated (usual Joomla installations with own files and database) but all slaves will load users, usergroups and access level tables from master site, hence these data will be always same on all sites.

... setting per site. ⋅ Feature: improved and simplified dUI. ⋅ Feature: new content type 'Menus - Admin Navigation' helps to load backend menu from master if slave uses own tables for menus. ⋅ Change: PHP 7.2 as min. ⋅ Change: config files moved to domain ...

Even if a connection is possible, the database server is usually located in another network, hence all queries will take lots of time and affect page load. The site will be just unusable.

If you have SQL query to load all data, yes, you can have a table with users data.

... allows to execute custom PHP code on report SQL query. ⋅ Feature: new dropdown/radio/checkbox filter value setting 'Values SQL Query' to load default value(s) dynamically. ⋅ Feature: use  {user->field_XXX}  tag for custom user field XXX. ⋅ Change: 'Print Layout' setting ...

... show up on the component's phpBB Folder dropdown. Unfortunately, the component itself handles the folder routing based on the menu link used to load phpBB. Unless MightySites has a way of using the p8pBB Bridge component five different times to access different folders, I'm probably going to ...

You have to create virtual hosts manually, in this case you can load websites via full-feature domain names but not via http://localhost.