Use Tdarr! Grab the Server and then use your main PC and other PCs you have around as nodes. It’s fully automated once you set it up. Just point it to the libraries and it scans and converts. Completes a Arrs/Plex/Jellyfin setup

https://github.com/HaveAGitGat/Tdarr

Take a look at Cloudreve

Photoprism! Has a consume folder and handles large libraries well.

Normally I’d recommend Immich but Photoprism is a better fit for your use case