First off, I hope you and yours are okay. I have a good friend whose daughter recently moved to Nashville to teach.
Of course there are obvious things that can’t work without internet access, but with a little preparation (while you have internet access), Plex works fine for me in an offline situation. Here’s a How-To that shows you what you need to do:
Also, quite some time ago I found this walk-through that I found easier to follow. It was updated recently, so it should be good for the current versions of Plex:
