Finally, this service is back online! I got myself a new VPS:
I currently experimenting with updates. The VPS hosting this doesn't have enough space, so I use an external ("pay by the hour") host for updates. If all works out, I'll be able to provide monthly updates again with only a few hours of additional server time, and only a few minutes of my own time.
The VPS got upgraded to 16 TB bandwidth per month, and downloads reach almost 1 Gbit/s.