I working with the Microsoft Edge Dev browser (the last updated) and Microsoft Teams onLine with an Office365 account. I uploaded a Word file (docx) in a team and if I want to open the file in Word Online (the Microsoft Teams document viewer) or in Sharepoint, I have a viewing issue. You can see black screen here PrintScreen Word Issue
It doesn't work with Office documents neither (Word, Excel PowerPoint files).
But it works with older Office documents format (which are not built with openxml structure). So I supposed there is an issue for viewing openxml documents in Microsoft Teams with Microsoft Edge Dev browser.
I don't know if it's the right place to post that issue. I also post this article in Stackoverflow.com
Thanks for considering it.