Dear @LuckyD,
Welcome back to the Wefugees Community and thank you for reaching out to us.
I am not too familar with the so-called "Daueraufenthalt-EU" but as far as I understand you can apply for it next to the Niederlassungserlaubnis. So you may hold both titles instead of changing. Most probably you also need to re-start the respective application process. Handbook Germany is providing a really good overview on the requirements - I recommend to check their website for more information (in various languages).
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,
Meike