Establish SELINUX compatibility

[phillxnet]

Further to #2699 and #2699 (comment) we have now further confirmation that openSUSE's upstream of SUSE is to favour SELINUX over AppArmor:

https://lists.opensuse.org/archives/list/[email protected]/thread/YN4TCBCU4A2V5G2MWR5EWYF46267BO7F/#YN4TCBCU4A2V5G2MWR5EWYF46267BO7F

Subject: RFC: SELinux as default MAC system on new Tumbleweed installations

The SUSE SELinux working group would like to announce the plan to
switch new Tumbleweed installations to SELinux as default MAC system
by the end of this year.

Directly relevant SELinux links:

• https://en.opensuse.org/Portal:SELinux
• https://en.opensuse.org/Portal:SELinux/PackagingCustomPolicy

Give we are now targeting the suspected last Leap 15 sub version of 15.6: our next most obvious upstream could be TW: given we already have this as a target. Hence this issues relevance.

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Thanks again to @FroggyFlox for pointers on this coming change in at least our TW targets.