(can't send the carriage return properly so \r it is here instead of ^M)

I am able to get an article buffer that still has the base64 encoded
signed blob in it but after it the verified content.

I have no idea where gnus normalizes the line endings to just newlines
and why the mm-view-pkcs7-get-type adjustment is needed. But calling
gnus-ime-display-part is of course not the right approach here. First
there should be some check if the decrypted content needs to be parsed
and handled again but I have no idea which function to write or feed the
decrypted content to.

I hope this may be helpful

Best regards
Sebastian