As with most apps in the Fediverse, the system first makes you connect to your server's web page to authenticate and authorize the app. Did you manage to get to that stage?
Informapirata
I couldn't figure out the problem, until I realized there was a space at the end of the link
No, but there is an app for Lemmy, made by the same developer: https://github.com/LiveFastEatTrashRaccoon/RaccoonForLemmy/releases/tag/1.13.0-beta01
Is he back to normal now?
When you write from Friendica (or another social network) to post on Lemmy, you must respect some basic rules.
Here I tried to write a handbook (in Italian) to help users write posts that have a readable title and work well
Furthermore, as regards the titles, you must take into account that Lemmy only interprets up to 200 characters; when exceeding 200 characters, the title is truncated. To count the characters, however, you have to consider the BBCode characters of the source text, which are converted into Markdown in Lemmy. So you have to be careful that "marked" text strings don't end up at the 200th character! Here are some additional notes:
Yes, they are two different apps:
Friendica: https://f-droid.org/it/packages/com.livefast.eattrash.raccoonforfriendica/
Lemmy: https://f-droid.org/it/packages/com.livefast.eattrash.raccoonforlemmy.android/