On the electron part, it's common to (ironically) not support Linux. There are pretty annoying bugs with windows management (window will stay stuck in the background), build process are always OS specific, etc.
So often not worth the maintainance.
The practical reality of distributing is mildly complicated, but there's now lots of good cross-distro options, and not having to deal with code signing everything makes some parts much easier than Mac & Windows. Ignoring that many users is fair enough for a startup or first MVP, but quite surprising for a company at Anthropic's level.