Well, I finally got Channels DVR installed and running in docker. I kept trying to figure out how to get the latest database backup from the old server into docker so I could restore the database, and gave up because I just couldn't figure out how to do it. I decided to just start setting up everything from scratch.
I added my HDHomeRun source with no problems. Also Sling TV with no problems. Tried to add Xfinity and it kept giving me a "not in subscription" error, despite the fact that I'm using the same login credentials as I described previously. Xfinity source still runs fine on my Raspberry Pi. Any idea why I can't add it as a source in docker on my Synology?
[side note - Xfinity Now came with my internet when I signed up for it, if anyone is wondering why I have both Xfinity and Sling TV]