尝试为 mediawiki 设置安装php-mbstring。
第一次尝试后已添加 Universe 存储库：Ubuntu 18.04 中缺少包 php7.2-mbstring
但让我很难在这里详细信息：
usertilo@myserver4:~$ sudo apt-get install php-mbstring
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages …