I am, and have been, relying on Transportr in multiple European countries, and it's been a joy. Only problem I've had is that additional information from the provider (temporary changes on the route etc.) isn't there, but that's no biggie. Sad to hear it's been unmaintained, hoping it'll keep working. Though, forking and updating the APIs for future broken providers wouldn't be too troublesome, right?

There's also Öffi which was last updated on F-Droid 16 days ago. It does pretty much the same job as Transportr, though it visualises the overview of journeys in a different graphical way than the list of Transportr, which is why I liked Transportr better. However, Öffi has some other neat features that Transportr doesn't have, such as listing the upcoming departures for all nearby stations/stops at once, based on your location.