I also run a Dell XPS 9575 2 in 1, with BIOS 1.40 and my system is *not* exhibiting this particular problem after a fresh 19.04 install. Keyboard and mouse work fine with GDM, but this is also after booting with the nomodeset kernel boot parameter.
Note: for other folks reading this thread wondering how I even got 19.04 installed, I had to install with nomodeset because of a kernel bug with the i915 module with certain laptop panels. I don't think the 4K panels are impacted by this bug...
I also run a Dell XPS 9575 2 in 1, with BIOS 1.40 and my system is *not* exhibiting this particular problem after a fresh 19.04 install. Keyboard and mouse work fine with GDM, but this is also after booting with the nomodeset kernel boot parameter.
Note: for other folks reading this thread wondering how I even got 19.04 installed, I had to install with nomodeset because of a kernel bug with the i915 module with certain laptop panels. I don't think the 4K panels are impacted by this bug...