1.
After setting up unattended-upgrades package Trac did not work anymore. But apt-get install python-setuptools did the trick.
2.
Drupal did not work correctly after transferring to the new virtual server. So was its main website, Gruppe Phänomenologie, but I managed to revive it. There was some issue with cached css and js files, so no css information was rendered.
- Since I could not access admin (reCaptcha was part of css) I had to switch off reCaptcha module by SQL query
- Afterwards I could log in as administrator and emptied all caches. Additionally I corrected the file paths
- Now the only problem is the captcha module / the reCaptcha login
