[Merge] lp:~frank-heimes/installation-guide/ubuntu-18.04-s390x-chapter_4_and_more into lp:~ubuntu-core-dev/installation-guide/ubuntu

[Frank Heimes]

Forgot to mention that I also fixed some minor parts in the guide where Debian specific things don't apply to Ubuntu ...
-- 
https://code.launchpad.net/~frank-heimes/installation-guide/ubuntu-18.04-s390x-chapter_4_and_more/+merge/347551
Your team Ubuntu Core Development Team is requested to review the proposed merge of lp:~frank-heimes/installation-guide/ubuntu-18.04-s390x-chapter_4_and_more into lp:~ubuntu-core-dev/installation-guide/ubuntu.