Any way possible to downgrade to iOS 13.3, on iPhoneX running 13.3.1

Oo'L if it's not being signed. You'll need to find a device that hasn't been updated to test with, instead.

I know a lot of people that are also looking to roll back due to the issues that 13.3.1 has caused for Apple developers with free accounts. The update has now prevented them from installing their apps on their devices for testing. I got lucky and managed to get it done withing the window, however this is still only a temperary fix. I don't know if 13.4 will fix this issue.

I really believe that Apple should have left the signing window open longer due to this issue.