This is an know issue, you have to downgrade your jerboa app, or wait for either an update of the feddit instance or an fix on the app side (which I guess won’t happen).
This is due to a breaking change in the API of the Lemmy backend, in version 0.18.
And feddit will wait for 0.18.1, because of problems they experienced with 0.18.
Unfortunately, you can only downgrade Jerboa to the former version or wait for feddit.de to be updated to Lemmy 0.18. The latest Jerboa version is currently not compatible with feddit.de which is running Lemmy 0.17.4.
You can also browse the mobile web version of feddit.de while waiting. That's what I am doing atm.
It's a feddit issue. They probably haven't upgraded to v0.18 yet and are waiting on 0.18.1. In the mean time check out some of the other apps available, I use liftoff