ELSTER is one of the few examples that come into my mind in terms of "software done right": It's stable and "just works", at least for me.
It's first version was released to the public in 1999, so... Yes, ELSTER is around for almost 20 years now, getting constantly refined at least in the front-end.
All in all, it's something you wouldn't have expected here in Germany in terms of software projects from the government.
AFAIK, it is mostly developed in-house, at least the original version was developed by the Bavarian tax office. In my experience, if government software (for schools, tax offices, political participation, etc.) is developed by an external company, the primary objective of the company often quickly transforms from "creating usable software for all citizens" to "drain the most amount of money out of the infinite resources of the federal government".
It's first version was released to the public in 1999, so... Yes, ELSTER is around for almost 20 years now, getting constantly refined at least in the front-end.
All in all, it's something you wouldn't have expected here in Germany in terms of software projects from the government.