Specified native messaging host not found.

I had the problem on Linux with Chromium:

Specified native messaging host not found.

The reason for the problem was that I the native messaging host manifest file in /etc/opt/chrome/native-messaging-hosts/ and ~/.config/google-chrome/NativeMessagingHosts/ - but Chromium uses chromium instead of google-chrome as app config name.

The error vanished when I used ~/.config/chromium/NativeMessagingHosts/.