@zaku49
Hi there, you are welcome to the Microsoft Edge Insider Community Hub!
This is an old issue. It happens also in Google Chrome. The white screen appears because the browser starts loading things it needs at the startup but it is a flash for you because your hardware specs are good to do these things in a fraction of a second. It also happens when you are opening a PWA, new tab or visiting the homepage. The Microsoft Edge team is investigating this issue. It would be better if you send feedback through the in-app feedback tool (Alt+Shift+I) in Microsoft Edge with the diagnostics attached which will help the Edge team to resolve this issue as soon as possible.