Resolved [URGENT] Can't make game fill all available space

If I try to resize the game to fill all available space on the screen, the game goes black. I tried messing with the unityContainer div and the #canvas canvas, to no avail. Now, I am aware there is a free webgl template on the asset store, but it doesn't work. Fullscreen button isn't an option because it doesn't work on iPhone. And I also know that if I turn the phone to landscape mode it works, but I need to do this in portrait. Attached is a gif showing the problem. Thank you for your time!

 

There's a template here, you can look at the index.html file and the css file.
https://github.com/De-Panther/unity-webxr-export/tree/master/Assets/WebGLTemplates/WebXRFullView