Remotes: Can a local Drush 8 be used to send commands to a remote Drupal 8.4 site which includes Drush 9? Let's say we have a dev-ops administrator who isn't a developer and doesn't want or (normally) need a local copy of the website.

As of Drupal 8.4, Drush 9 is required, and Drush 9 doesn't have a way to install it globally. But Drush 8 still does.

So the question is, can someone use Drush 8 locally with aliases for a remote Drupal >8.4 site with Drush 9 as a dependency?

If not, then, is there another way someone can use a local Drush 9 without building the entire site?

What's the best practice for someone who needs to run Drush locally to control remote sites in the Drush 9 world, where "someone" means someone who isn't working on a local copy of the site?
I would assume install drush 9 locally to a project, but still use alias files for all your remote systems. eg, treat the local installation as a globally installed service conceptually.

if you dont like a random project on your system hosting drush this way stick it on a VM or Container and interact with drush there.