The best replacement for file manager is es file explorer.

The best alternatives to file manager are rated as following:
★★★★★  es file explorer
★★★★★  androzip
★★★  astro
★★★  astro file manager
★★★  file aid
★★  x-plore
★  linda file manager
★  file manager
  legacy file manager
  root explorer

Your alternative for file manager is not listed? Suggest!
Speaking about file manager, one probably shouldn't forget about ckeditor.

Other search terms related to file manager and their ratings are:
★★★★★ ckeditor
You have in mind a companion for file manager and it is not yet here? Propose!



Google Trends

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file manager
es file explorer
androzip