[thek3nger]

I update it with Brew on macOS and Scoop [1] on Windows (but I guess it is included in other package managers such as chocolatey).

Of course, a built-in auto-updater would be good, but a packaged version is a nice workaround for me.

[1]: https://scoop.sh/

[dopa42365]

It's also on the official microsoft package manager (winget).

https://github.com/microsoft/winget-cli

[crtasm]

It is: https://community.chocolatey.org/packages?q=calibre