I have been asked to help a client upgrade their Magento site from v2.1.9 to v2.2.3 but from what I'm reading on the magento.com website so far, this sounds like a very complex process that depends on factors such as the installation method that was originally used for this instance of Magento and it requires more specific version info than I can find in the Magento admin pages. It appears attempting the upgrade without knowing this information is likely doomed to corrupting their installation.
How can I discover from looking at a Magento v2.1.9 website 1) whether it was installed by "cloning from github", "web setup wizard", or "command line"? and 2) whether their Magento v2.1.9 is a Magento v2.1.9EE or Magento v2.1.9 community edition / open source edition?
I have explored the Admin pages but the only version info I've found is "Magento ver. 2.1.9". Since the upgrade documents indicate it's critical to know this stuff before attempting an upgrade, I'm assuming it's here somewhere and I'm just missing it! If someone with more Magento experience could point me to the correct Admin page to see these details, I'd really appreciate it.