What is OPDS
OPDS is a standard for content distribution. Most popular comic servers have adopted OPDS to allow third-party apps to access their content.
If you have a large comic collection or you just don't want your files to take out too much space in your device, you can choose to have your content stored on iCloud Drive or have it stored in your own server.
Panels can connect to server using the OPDS standard. There are multiple server implementations compatible with OPDS. For comics in particular, we do recommend using Kavita, Komga or Codex.
Each one of those servers offer great documentation and communities around them, so we strongly suggest you visit them to set your server up.
You can also check out the guides we've written for some of the most popular comic servers.