You can use any version of the CMS without a Docker install.
I would strongly recommend upgrading your CMS to the Latest version (currently 1.8.11), not just for PHP 7.1 support but also because many bugs will have been fixed since 1.7.9, as well as the features that have been added to CMS, for example XMR.
Below is a link to our Custom Installation upgrade Guide, which will help to understand how to upgrade your CMS:
Thanks. The reason I questioned the support for PHP 7.1 was that all I could find was a statement around 1.8.0 where you wrote something like “support for PHP 7 will be announced when it is available”.