Just a quick comment,
Simple English ('Simple') is the only simplified language version running under that name.
For German there are a few initiatives 'Einfaches Deutsch/Vereinfachtes Deutsch' or similar; they mainly target the problem of 'functional analphebetism' though, and to my knowledge, none has reached a status where a 'Wikipedia Version' could be created.
There were 3 simplified versions used in the German colonies ('Kolonialdeutch', 'Weltdeutsch', and 'Unserdeusch'; the first two are planned languages, like Esperanto, that never caught on, the last one is essentially Tok Pisin with a German vocabulary - there are less than 500 speakers worldwide, most live in Australia).
In short - none of the German versions lend themselves to creating a wikipedia.
French -I think there are two attempts at creating a Simple French Wikipedia, but both stalled.

I think you can close this, this is not a problem of the software.

Just a quick note:

• this is probably not about the translation tool, creating a normal article (andd adding iw links I get the same problem)

The actual text that is generated is:
More than one of <code style="color:inherit; border:inherit; padding:inherit;">&#x7C;work=</code> and <code style="color:inherit; border:inherit; padding:inherit;">&#x7C;journal=</code> specified ([[Help:CS1 errors#redundant parameters|help]]); More than one of <code style="color:inherit; border:inherit; padding:inherit;">&#x7C;DOI=</code> and <code style="color:inherit; border:inherit; padding:inherit;">&#x7C;doi=</code> specified ([[Help:CS1 errors#redundant parameters|help]])
[[Category:Pages with citations having redundant parameters]]
[[Category:Pages with citations having redundant parameters]]

This issue is probably not related to the content Translation tool, but perhaps to the mechanism interwiki links are calculated.
Also compare the image below, to find a case where a page has been newly created on SEWP, and Interwiki links were later added.

Even if this is the case, the situation as described above should not happen. At the time when I copyedit an article for last cleanup, it must have been saved, so it likely exists on SEWP. At that time, the software should not tell me the trandation to the language I am currently editing is missing; No matter what: In the In other langauages, my own language must never show up, neither as missing, nor as present.

I just wanted to add a comment: Perhaps this is an issue related to page refresh. Approximately half a day after creation, the language links ("In other languages", in the image) show up correctly (that is without the non-existent link to SEWP).