After a few more gray hairs and a number of curses I have finally managed to link my cloud via WebDAV over SSL as a network drive in Windows.
The main problem was the self-signed certificate.
On Windows the certificate needs to be installed and declared to be safe.
Finally these steps worked for me.
After some complications, he is now finally here - the Banana Pi.
Again, the precondition is a LEMP installation as described in this article: Installation of Nginx, MySQL and PHP
Seafile has a its own little web server, but it can not handle the HTTPS protocol. So, to get an encrypted transmission to the cloud, you have to run Seafile behind a "real" web server - in this case, nginx.
The installation is done in 4 steps:
Seafile is an open-source cloud solution and on a BeagleBone or Raspberry a really good alternative to OwnCloud (see the article OwnCloud alternative with Seafile and Baikal ).
Seafile is now running on my BeagleBone Black for a few months and I must say that it is working very reliable since now. Meanwhile, around 600 GB of data are in the cloud and I have found no problems yet.
Now that I finally had my little server, I wanted to sync all my stuff from a variety of electronic devices: ie the working files on different computers, and also the calendar data and addresses should finally be in sync on all devices.
After a quick search I am first came to OwnCloud. A truly worry-free solution and also really easy to install.
OwnCloud offers: