Try to install php-mbstring for mediawiki setup.

already added after first attempt universe repository: Package php7.2-mbstring missing in Ubuntu 18.04

But gives me hard time
Here details:

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 have unmet dependencies:

 php-mbstring : Depends: php7.2-mbstring but it is not going to be installed

E: Unable to correct problems, you have held broken packages.



usertilo@myserver4:~$ sudo apt-get install php7.2-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 have unmet dependencies:

 php7.2-mbstring : Depends: php7.2-common (= 7.2.3-1ubuntu1) but 7.2.7-0ubuntu0.18.04.2 is to be installed

E: Unable to correct problems, you have held broken packages.



usertilo@myserver4:~$ uname -a

Linux myserver4 4.15.0-29-generic #31-Ubuntu SMP Tue Jul 17 15:39:52 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux



usertilo@myserver4:~$ lsb_release -a

No LSB modules are available.

Distributor ID: Ubuntu

Description:    Ubuntu 18.04.1 LTS

Release:        18.04

Codename:       bionic



usertilo@myserver4:~$ sudo apt-get install -f

Reading package lists... Done

Building dependency tree

Reading state information... Done

0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.



usertilo@server4:~$ sudo apt-get install php7.2-common

Reading package lists... Done

Building dependency tree

Reading state information... Done

php7.2-common is already the newest version (7.2.7-0ubuntu0.18.04.2).

0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

• update add info requested from comments

usertilo@myserver4:~$ sudo apt-cache policy php7.2-common php7.2-mbstring

php7.2-common:

  Installed: 7.2.7-0ubuntu0.18.04.2

  Candidate: 7.2.7-0ubuntu0.18.04.2

  Version table:

 *** 7.2.7-0ubuntu0.18.04.2 500

        500 http://archive.ubuntu.com/ubuntu bionic-security/main amd64 Packages

        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages

        100 /var/lib/dpkg/status

     7.2.3-1ubuntu1 500

        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

php7.2-mbstring:

  Installed: (none)

  Candidate: 7.2.3-1ubuntu1

  Version table:

     7.2.3-1ubuntu1 500

        500 http://archive.ubuntu.com/ubuntu bionic/universe amd64 Packages



usertilo@myserver4:~$ cat /etc/apt/sources.list

deb http://archive.ubuntu.com/ubuntu bionic main universe

deb http://archive.ubuntu.com/ubuntu bionic-security main

# deb-src http://archive.ubuntu.com/ubuntu bionic universe

deb http://archive.ubuntu.com/ubuntu bionic-updates main



usertilo@myserver4:~$ cat /etc/apt/sources.list.d/*

cat: '/etc/apt/sources.list.d/*': No such file or directory