However Sparkassen, Deutsche Bank etc all refuse to work on Lineage OS at all *without any actual root solution installed*. I actually don't want any root access, I can use recovery mode and even write special permission XMLs if certain apps need it.

I just don't want bundled Google Dialer etc in stock ROMs that is feeding more data to Google about me and my loved ones. I keep my and my family's contacts in a private cloud solution. I don't use GMail for private e-mails. Nor Google Calendar. Removing these apps break stock ROMs due to special permission modifications Google did. Lineage OS is my escape but the stupid banks reliably choose stupidest security theather solutions that you were forced to implement.