What drivers are you using?

I'm running Chrome 72 at 4K on a 50" monitor via KDE Plasma and Fedora 29 on Kernel 4.20, using only an AMD Ryzen 5 2400g ASIC, and it runs just fine (so it does work on the desktop in at least that configuration). I did however manually build the latest ROCm [1] and Vulkan [2]. I would check your flags and check your settings to make sure you have the right optimizations.

  chrome://flags  chrome://chrome-urls

BTW: For whatever reason, in certain builds under some combination of settings, the times I've experienced Chrome running at a crawl, it's usually been an issue with GPU rasterization. These are the settings I have disabled (everything else is set to hardware accelerated or enabled)...

  chrome://gpu

  Out-of-process Rasterization: Disabled
  Hardware Protected Video Decode: Hardware accelerated
  Rasterization: Software only. Hardware acceleration disabled
  Skia Deferred Display List: Disabled
  Skia Renderer: Disabled
  Surface Control: Disabled

Here's my full Command Line:

  /usr/bin/google-chrome-stable --disable-gpu-driver-bug-workarounds --enable-native-gpu-memory-buffers --force-device-scale-factor=1 --enable-accelerated-video --enable-accelerated-mjpeg-decode --flag-switches-begin --enable-audio-focus --enable-experimental-web-platform-features --enable-google-branded-context-menu --enable-oop-rasterization --enable-quic --enable-zero-copy --ignore-gpu-blacklist --enable-lcd-text --load-media-router-component-extension=1 --enable-hardware-overlays=single-fullscreen,single-on-top,underlay --enable-features=DrawOcclusion,ExperimentalProductivityFeatures,FontCacheScaling,InfiniteSessionRestore,LayeredAPI,NetworkService,OverlayScrollbar,OverlayScrollbarFlashAfterAnyScrollUpdate,OverlayScrollbarFlashWhenMouseEnter,PageAlmostIdle,ProactiveTabFreezeAndDiscard,SharedArrayBuffer,SiteCharacteristicsDatabase,UseSurfaceLayerForVideo,V8Orinoco,V8VmFuture,VizDisplayCompositor,VizHitTestDrawQuad,WebAssemblyBaseline,WebAssemblyThreads,WebRTC-H264WithOpenH264FFmpeg,enable-pixel-canvas-recording --flag-switches-end

[1] https://github.com/RadeonOpenCompute/ROCm

[2] https://github.com/GPUOpen-Drivers/AMDVLK