DOOM Eternal won't launch - amdgpu driver won't run Vulkan

I downloaded DOOM Eternal last night after it "unlocked" on Steam. However, I have been unable to launch the game. A quick check on Google indicates that OpenGL is not an option as with DOOM 2016; Vulkan is the only game in town.

I Googled this problem and came across this thread. However, after implementing both dive's and bassmadrigal's suggestions, there has been no change. DOOM Eternal still won't launch. I am at my wits' end. I would appreciate any suggestions. Thanks!