@girish unfortunately the server which I would not advice and therefore never posted a reply. After proof of concept was successful I decided to not use it in production. In the end it's Brothers fault that they do not offer other methods or current security standards.
My current setup looks like this:
One button at my printer is programmed to scan to an local (can also be a network folder in case you have many clients) folder on my client PC. I then use RealTimeSync (part of the open source software FreeFileSync) running as a system service to sync the folder to one of my Nextcloud folders. This Nextcloud folder is just a mount to an external storage which I also use as base document directory for Paperless. So what happens is the new PDF file automatically gets transfered to Paperless, is processed and pushed into Nextcloud including OCR layer, tags and other automation workflows.