Got past the purple screen of death using the nomodeset header at GRUB.
However, when I check if the rx550 is being used with lshw | grep AMD, only the processor and some micro devices get listed.
Since I use LXDE and I needed to get final confirmation that I don't have the right drivers, I logged out and then in with the GNOME desktop environment and clicked on Settings > About, then it turned out that my Ubuntu installation was using the APU instead of my GPU.
Reading up on the issue from forum posts and https://help.ubuntu.com/community/RadeonDriver tells me that the rx550 is only supported on Ubuntu 16.04.3 LTS (and so does the official AMD drivers page for Linux https://support.amd.com/en-us/download/linux).
Since the new amdgpu-pro drivers were released a couple of months back, I was wondering if there are any updates on whether there's a way to get 17.10 to work with the rx550?
I've read up on all materials that I can find, and I am on Stack Overflow basically every day because of my work (WebDev, with very limited SysAdmin experience), so I decided to ask here.