How to Discover a Subtle Startup Catalyst?

I'm interested in understanding how the OperaGX Browser app initiates upon computer login. Despite examining the user Startup folder, the All Users Startup folder, and searching for a service, I have been unable to determine its startup method. Specifically, I am seeking information within Windows 10 that specifies the app's activation upon Windows startup or login, rather than a setting within the application. My goal is to prevent its launch using a tool like Group Policy.