Calibre is great but it’s not a server based program, it’s just a desktop client. There is Calibre-web which you can host which kinda turns it into a server but it does that by exposing a website you connect to that shows you the Calibre interface via VNC, so it’s a bit hackey.

I haven’t tried it but https://www.kavitareader.com/ might be a good alternative if you end up not liking Calibre.