Hi all,
found it for myself. It was the file /etc/plymouthd.conf, which somehow was overwritten.

I am not sure, why this happened, it must have happened by an upgrade. The entry changed from "kali" to "emerald" and added some lines more.
For me it looks, as some package had overwritten this file. As I got a working kali on another pc I could compare both.

After editing /etc/plymouthd to the same as on the working computer and updated initramfs, everything is working as normal again.

So this issue can safely be closed.

Thanks to all, who read this.

Best regards

Hans

Closing as user found the issue in their configs.