I feel that I'm usually more upset that apps choose electron and I have performance issue because they didn't spend time writing a proper lightweight desktop application. I feel like Calibre is actually one of those apps.
I could see portability across devices being useful but is the Calibre interface really going to be conducive for that?
All the other services I have running are on a server in my closet, which I access with a web browser from other devices. Calibre needing to run on my workstation is a big shift in that workflow. Especially because all the rest of my media is sitting on that server.
Also, UX of open source desktop apps is… lacking. They don’t look good, and they don’t feel good to use. But that might be because I’m picky and spoiled by decades of using a Mac.
I definitely don’t want more Electron apps. About the only things I want to run locally is a browser, a text editor, and a terminal.
You can use Podman too, if that would be a problem.
Look at StirlingPDF if you want an example how to run OR are interested in a great web-UI PDF editor based off various open sourc tools, in a single interface
ePub is basically just a limited HTML page in a zip file (plus a bunch of metadata and CSS styles), and ePub 3 can contain audio and video elements embedded in the text, just like a webpage. With the most basic usage, it would just show up as an audio player in the middle of the text, no sync. But there is also a media overlay thing I haven't looked much into that looks like it provides sync.