There are generic file modification modules and states in SaltStack.
For example, you could use file.replace:
salt '*' file.replace /etc/zypp/zypp.conf pattern='solver.allowVendorChange = true' repl='solver.allowVendorChange = false'
In case the line doesn't exist at all, you can append it to the configuration in a state using file.blockreplace:
file.blockreplace:
- name: /etc/zypp/zypp.conf
- marker_start: "#BLOCK TOP: Salt managed entry, do not edit!"
- marker_end: "#BLOCK BOTTOM: End of Salt managed entry"
- content: |
solver.allowVendorChange = true
- show_changes: True
- append_if_not_found: True