I have been using pywinauto for automation of desktop application. This tool was fine until we started using Sciter (see https://sciter.com for more info) on some screens. Pywinauto supports Win32 API, MS UI interfaces but Sciter is HTML based UI framework, so they are not compatible.
I found the next info here https://sciter.com/forums/topic/how-to-automate-sciter-ui-is-it-supports-to-seleniumqtp-for-automation/
Sciter exposes UI Automation interfaces and IAccessible (/engine/win/win-accessible.h) so tools that know about them can be used