Storyboard launch issue following Unity update

Hi Everyone,

Realise I might be a bit late to the party with this one... but having an issue with launching on iOS following a recent move from 2019.1.10 to 2020.3.1...

When setting up the project in Unity I can select either "None" or add an image under "Image and Background" either constant or relative size in the Launch/Splash Screen settings. I then build out and open the Xcode Workspace.

In the Xcode workspace I can see the .storyboard, I can see the images if I use that option, however when I archive and push to testflight the game launches and just hangs on said screen/image.

I'm sure I'm missing a setup stage in xcode or something however documentation is scarce and my google skills aren't turning much up... if anyone could point me in the right direction it'd be greatly appreciated.