Yup you really need to mash it, ok I have a console.
This might be a clue:
drm:amdgpu_init [amdgpu] *ERROR* VGACON disables amdgpu kernel modesetting
On Tue., 21 Aug. 2018, 08:10 Auke Kok, <auke-jan.h.kok(a)intel.com> wrote:
On 08/20/2018 02:46 PM, Richard Thornton wrote:
> Thanks, I have no idea how to access the kernel command line, the system
> boots quickly and I see no prompts to press a key?
Yes, you essentially have to mash `space`. Escape should work too, but
may cause the BIOS screen to show instead of the bootloader.
Once you boot once, you can modify the bootloader to use a longer
default timeout (`man systemd-boot`).