Flexi is built specially for one gallery at a time but this doesn’t mean you cannot include multiple gallery on same page.

Just you have to take care of some of the settings & shortcode so that the gallery do not get conflict with each other because same javascript, ajax call will be repeated on the same page.

Shortcode
If you are using shortcode then just add a parameter clear=”true” into it. It will deactivate the navigation and add unique identity to the each gallery and popup.
Eg.
Gallery of album 1


Gutenblock Builder (Visual Builder)
Since block builder is GUI based and shortcode is automatically generated at background you cannot add clear=”true” to it. Hence there is a tool which need to be enabled.