I was late to #freesoftwareadvent so decided just to follow and see what others suggested.

However after 21 days I've only seen one mention of a file manager.

So I'm going to mention 2.

When I'm working on a headless Linux server 99% of the time i install midnight commander
https://midnight-commander.org/

On Mac, Windows or Linux with a desktop I install Double Commander.
https://doublecmd.sourceforge.io/

Both are 2 pane file managers with built in viewers, editors and compressed file support.