I've developed DiscChanger.NET, a free ASP.NET Core 3.1 solution to manage the discs in DVP-CX777ES and BDP-CX7000ES changers. I use my DVP-CX777ES disc changers almost exclusively for audio, since they still hold their own in 2020, with SACD and regular CD support. The program can run on Windows (IIS) or Linux and I've tested it on Windows 10 and on a Raspberry Pi 4. A Raspberry Pi 4 has up to 5 serial ports and can control 5 changers out of the box. Probably more if you add USB serial ports but I have not tested how much of a load it can handle.
DiscChanger.NET uses MusicBrainz to lookup the disc data given the table of contents from the changer serial RS232 interface and organizes the discs in a grid, making it convenient to use any of your tablets or computers to select discs or tracks to play.
DiscChanger.NET also shows BD and DVD, but is not yet capable of performing metadata lookups for these disc types. It is an open source project and any contributions are welcomed.