I figured it out.
This can be done with a single module and standard WP functionality.
In the post, click on the left side, there is a create gallery link there.
For them to display more nicely, use the https://wordpress.org/plugins/jquery-colorbox/ plugin.
That’s it.
It was so simple stupid that I could not imagine it could be done so easily…so I was fishing for tons of plugins for no reason;)