Brand new to Kodi and Linux

I am brand new to Kodi and Linux and am struggling with getting it to do what I expected it’d do out of box.

I have Kodi running and inserted a thumb drive with an .mp4 video on it. I expected I’d be able to see the thumb drive and/or Kodi would see it and say the file is available. Neither of those things happened.

How do I get to the thumb drive? I’m used to Windows where the drives are all enumerated and automatically appear.

Is Kodi able to natively play .mp4 files? If not, will it play .mkv files?

My Roku boxes can all see my Plex Server. Am I able to have Kodi see the Plex Server? If so, how?

I’d like to have my Kodi player also be able to play the files on the Plex Server without those files being served up by Plex. My Windows box is able to communicate with the Plex Server (a Linux box) as the Plex Server uses Samba. I’m not able to have the Kodi Player see the Plex Server’s files. How do I do that?

Thanks in advance.

Kodi on OSMC currently doesn’t support browsing of Samba shares. You either would need to add them manually with smb://server/share
Alternatively (and more performant) use fstab based mounting of smb shares