Missing graphics drivers for AMD Ryzen 5 with Radeon Vega 8

I have recently installed Ubuntu 19.04 on an ASUS TUF Gaming FX505DY laptop. The laptop has a AMD Ryzen 5 with Radeon Vega 8 processor.

No warnings where raised during the installation process regarding problems with the graphics driver. When I connected a HDMI connected monitor I found it did not work.

I have attached the graphics driver logs

========================================================================== cat /var/log/gpu-manager.log

log_file: /var/log/gpu-manager.log
last_boot_file: /var/lib/ubuntu-drivers-common/last_gfx_boot
new_boot_file: /var/lib/ubuntu-drivers-common/last_gfx_boot
can't access /run/u-d-c-nvidia-was-loaded file
can't access /opt/amdgpu-pro/bin/amdgpu-pro-px
Looking for nvidia modules in /lib/modules/5.0.0-27-generic/updates/dkms
Looking for amdgpu modules in /lib/modules/5.0.0-27-generic/updates/dkms
Is nvidia loaded? no
Was nvidia unloaded? no
Is nvidia blacklisted? no
Is intel loaded? no
Is radeon loaded? no
Is radeon blacklisted? no
Is amdgpu loaded? no
Is amdgpu blacklisted? no
Is amdgpu versioned? no
Is amdgpu pro stack? no
Is nouveau loaded? no
Is nouveau blacklisted? no
Is nvidia kernel module available? no
Is amdgpu kernel module available? no
Vendor/Device Id: 1002:67ef
BusID "PCI:1@0:0:0"
Is boot vga? no
Error: can't access /sys/bus/pci/devices/0000:01:00.0/driver
The device is not bound to any driver.
Vendor/Device Id: 1002:15d8
BusID "PCI:5@0:0:0"
Is boot vga? yes
Error: can't access /sys/bus/pci/devices/0000:05:00.0/driver
The device is not bound to any driver.
Error : Failed to open /dev/dri
Error : Failed to open /dev/dri
Error : Failed to open /dev/dri
Error : Failed to open /dev/dri
Does it require offloading? no
last cards number = 2
Has amd? yes
Has intel? no
Has nvidia? no
How many cards? 2
Has the system changed? No
Unsupported discrete card vendor: 1002
Nothing to do

============================================================================== sudo lshw -C display
  *-display UNCLAIMED
       description: Display controller
       product: Baffin [Radeon RX 460/560D / Pro 450/455/460/555/560]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:01:00.0
       version: e5
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi cap_list
       configuration: latency=0
       resources: memory:e0000000-efffffff memory:f0000000-f01fffff ioport:f000(size=256) memory:fea00000-fea3ffff memory:fea40000-fea5ffff
  *-display UNCLAIMED
       description: VGA compatible controller
       product: Picasso
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:05:00.0
       version: c2
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi msix vga_controller bus_master cap_list
       configuration: latency=0
       resources: memory:c0000000-cfffffff memory:d0000000-d01fffff ioport:c000(size=256) memory:fe500000-fe57ffff

********************************************************************************* QUESTIONS

1. Why is the problem with unsupported drivers not flagged during the installation process? The default driver does work for the laptop's monitor, but will not drive a second monitor attached to the HDMI port

2. I have seen reference to a general purpose AMD graphics driver, but there is no reference to this driver being supported on Ubuntu 19.04. If I went ahead and attempted to install the general purpose graphics driver, how would I back it out if it did not work.

I have raised this issue as a "question", but I think it is probably a bug but I could not find out how to raise a bug associated with a lack of device drivers.