On the official website of AMD I couldn't find the drivers for Ubuntu, only for Windows 10 (AMD Ryzen 5 Driver). I can't change my screen resolution, just one option available.
I tried a lot of things; I don't have the /etc/X11/xorg.conf file probably because I can't install AMD drivers. I tried a lot of commands related to xrandr, but none worked.
I just bought the new 3400G and I run into the same problem
https://github.com/M-Bab/linux-kernel-amdgpu-binaries
Clone or download -> Download zip
sudo dpkg -i [linux-headers-name].deb [linux-image-name].deb firmware-radeon-ucode_*_all.deb
sudo update-grub
sudo reboot
Thats it I would like to give the kiss to whoever make that available man
I had similar issues with AMD Ryzen 5 3400g and Ubuntu 18.04. In my case I also wanted to connect second display. I spend hours working on the bios and different drivers to no avail. Finally I found the solution, just upgrade the kernel above 4.15. At the time of writing I managed to upgrade the kernel to 5.0. It really helped, I can change resolution and connect multiple displays.
To check what kernel you have:
uname -a
To upgrade kernel:
sudo apt install --install-recommends linux-generic-hwe-18.04 xserver-xorg-hwe-18.04
Finally reboot the system.
Neither upgrading to 5.0 nor installing the linux-kernel-amdgpu-binaries linked above worked for me. I finally got my system running as expected after installing the 5.4.12 kernel using ubuntu kernel utility tools and NOT installing any additional drivers under Ubuntu 19.04.
