Have you updated the BIOS? Annoyingly, this is something that usually needs Windows.
What version of Ubuntu MATE? 18.04 or 18.10?
Depending on what's on your startup disk, you may have hit the problem that the Ryzen APUs are new and only recent kernels know enough about them to run properly.
Step one
Edit the boot command line to have...
acpi=off
or if that doesn't work
pci=noacpi
before quiet nosplash
. This should allow it to boot.
Step two
Get a later kernel, either via updates or by downloading one from the Ubuntu mainline repository.
(Disclaimer: I am on stage one at the moment - the laptop is dumping the contents of its Windows partition before I replace them with Ubuntu MATE...)
For some reason, after installing the 1.09 BIOS (it came with 1.03...) having acpi=off
wouldn't allow it to boot. What did was having pci=noacpi
there instead.
That allowed me to boot with the Ubuntu MATE 18.10 startup, install it alongside Windows, boot to GRUB, edit the command line to have pci=noacpi
, and boot successfully.
I've edited /etc/default/grub
to add that parameter to the line beginning GRUB_CMDLINE_LINUX_DEFAULT=
, then run sudo update-grub
, so I no longer have to edit the command line by hand each time.
So far, it's working...
The only other thing I have needed to do is turn off the advanced setting for the touchpad in the BIOS, because it wasn't working in Ubuntu MATE until I did that.
This article may be helpful