feddit.de is in this error state since quite a while now (over a month). The web interface does not work anymore, but connecting through an app still works (I use voyager for example). Most people have migrated away from feddit.de to feddit.org. I will do the same at some point, I just didn’t have the time yet.
For opensource maps, it will be open street map. If it is outdated for you area, open a few issues, add a few things yourself, and you will notice that others will join to help.