Adding a new library takes days, weeks, months to show up

[TheDreadPirate]

You can access the logs in your dashboard.  Logs are near the bottom of the left panel.  log_20240911.log

Part of the problem is probably just the specs of your system.  A dual core Intel Gemini Lake CPU with, I'm assuming, 2GB of RAM.  I'm also assuming that Jellyfin is running on a hard drive.  Each of these is not ideal.

A couple of things you can do to speed things up.  In your library settings, did you enable trick plays and chapter image extraction?  If so, did you also enable generating trickplays and extracting chapter images on library scan?  If yes to either, you should disable both of them for now.