Update: The old one revived. So I have two plex serversToday my Windows 10 Plex Server died a blue screen motherboard death. I'm only struck by how long it lasted, as it started out as a Windows 7 computer used by our business, and when retired three years ago, I acquired it and turned it into a media server.
It accesses all the ,and music on my NAS device. My NAS device is my local backup server. Therefore, the media source for my server is actually backup. It works great.
So today I dragged another retired Windows 10 laptop out of my closet, got it up to date, and installed Plex. It was straightforward, except that I had remembered wrong taht I can point it to an external device. I couldn't figure out how to get my data!
That's not actually how it works. Apparently what I had done three years ago, and I did again today, is to go into file explorer, choose "Map Network Drive" and map my NAS device as a pc network drive. Then when I edited movies and music in my Plex Server app, I was able to point each to the movies and music I wanted on the network drive. Simple.