Comment 8 for bug 358283

> However, I could not find out how the notification is installed

That's explained in https://wiki.ubuntu.com/InteractiveUpgradeHooks : ship it in /usr/share/packagename and have the postinst copy it to /var/lib/update-notifier/user.d/.

I suppose update-notifier invokes gettext at runtime, and the "_" markers are just to enable .pot file building. Subscribing mvo to confirm, but it should work fine as it is. Doesn't it?

> * Variable substitution in .desktop.in files

This does not generally work as far as I know. You have to hardcode the domain name there (or use cdbs' langpack.mk which adds the field for you). However, the domain name shouldn't change, so if you just hardcode it it should be just fine.