Ansible 2.6.0 RC5 released last night.

Install instructions for Raspbian: (likely identical on Ubuntu 18.04)

apt install python-pip libffi-dev          (this line nec if virgin Raspbian)
pip install ansible==2.6.0rc5

Changelog: https://github.com/ansible/ansible/blob/stable-2.6/changelogs/CHANGELOG-v2.6.rst

Porting Guide: https://docs.ansible.com/ansible/devel/porting_guides/porting_guide_2.6.html ("stabilization release" for Ansible 2.5, so very few differences)

Ansible 2.6.0 is released @ https://releases.ansible.com/ansible/ansible-2.6.0.tar.gz

Changelog: https://github.com/ansible/ansible/blob/stable-2.6/changelogs/CHANGELOG-v2.6.rst

.debs / PPA's for Raspbian & Ubuntu are now live here:
https://launchpad.net/~ansible/+archive/ubuntu/ansible-2.6
http://ppa.launchpad.net/ansible/ansible-2.6/ubuntu/pool/main/a/ansible/

.debs / PPA's for Raspbian & Ubuntu should also appear here in coming days:
https://launchpad.net/~ansible/+archive/ubuntu/ansible
http://ppa.launchpad.net/ansible/ansible/ubuntu/pool/main/a/ansible/

After running `scripts/ansible-2.6.x" the newly released Ansible 2.6.0 ran "./iiab-install --reinstall" flawlessly on both:

• Raspbian Stetch on RPi3 B+
• Ubuntu 18.04 LTS/Server on a regular PC