Ultimate-Member plugin can be downloaded from here
The plugin makes it a breeze for users to sign-up and become members of your website. The plugin allows you to add beautiful user profiles to your site and is perfect for creating advanced online communities and membership sites.

Flexi plugin has option to add the tab at UltimateMember plugin where each individual profile will have gallery tab which contains all the post submitted by current user.

To achieve above features you must first install Ultimate-Member plugin and activate it.
After the plugin activation go to admin dashboard Flexi Gallery > Settings > Extension > Enable Ultimate-Member
Check below images for references

Note: Sometime even after above settings, tab doesn’t appear. This means Ultimate-Member not able register it’s new hook.
Just deactivate the ultimate-member plugin and reactivate it again immediately.