From the Store description:
Woopiti is a free universal file manager that allows you to access all your files no matter where they are, and perform countless actions such as upload, download, copy, move, delete, share, send by email, SMS or Bluetooth, among others. And if you forgot where your files are, don't worry, Woopiti has a search engine that searches across all your accounts.
Supports: Facebook, Dropbox, Google Drive, OneDrive, Youtube, Google Photos, Flickr, Twitter, Instagram, Box, Mega.co.nz, SugarSync, CloudMe, HiDrive, 4Shared, OwnCloud and WebDav.
Some screenshots to illustrate the app in action, this time under Windows 10 on the desktop (though it also works fine under Mobile):
Woopiti UWP is in the Store here. It's free with IAPs to remove some limitations.