Hello,
The Editor is built with Qt 5.11.3 which was released at the end of 2018. That version of Qt doesn’t receive updates and fixes anymore.
Qt5 itself will soon reach its end of life.
What will this mean to the Editor? Will it still work in the future? Are there plans to upgrade to something with longer term support such as Qt6?
We aim to support as old operating systems as possible (yes, there are still users of El Capitan 
), and to keep compatibility with the latest ones. As the Qt version we are using supports a wide array of operating systems, and is stable for our purposes, there’s no real need to upgrade and break compatibility for older OS releases.
There’s no need to worry really, a Qt build is bundled with every Editor release, whatever Qt version you have installed on your system should not have any effect, as the built-in one should be getting used for the Editor.
If any particular issues will appear on latest OS and hardware, we’ll release an update to address that.