I have a Dell Inspiron 5570, which has the same GPU with the one you mention.
Using any ubuntu 18.04 flavour (I've tested it with ubuntu-mate and xubuntu) it installs the amdgpu driver and is functional.
My issue with the specific GPU is that it performs far worse than the intel 620 one. With glmark2 I get for INTEL:
=======================================================
glmark2 2014.03+git20150611.fa71af2d
=======================================================
OpenGL Information
GL_VENDOR: Intel Open Source Technology Center
GL_RENDERER: Mesa DRI Intel(R) UHD Graphics 620 (Kabylake GT2)
GL_VERSION: 3.0 Mesa 19.0.1 - padoka PPA
=======================================================
[build] use-vbo=false: FPS: 450 FrameTime: 2.222 ms
[build] use-vbo=true: FPS: 459 FrameTime: 2.179 ms
[texture] texture-filter=nearest: FPS: 439 FrameTime: 2.278 ms
[texture] texture-filter=linear: FPS: 423 FrameTime: 2.364 ms
[texture] texture-filter=mipmap: FPS: 419 FrameTime: 2.387 ms
[shading] shading=gouraud: FPS: 422 FrameTime: 2.370 ms
[shading] shading=blinn-phong-inf: FPS: 418 FrameTime: 2.392 ms
[shading] shading=phong: FPS: 419 FrameTime: 2.387 ms
[shading] shading=cel: FPS: 416 FrameTime: 2.404 ms
[bump] bump-render=high-poly: FPS: 407 FrameTime: 2.457 ms
[bump] bump-render=normals: FPS: 428 FrameTime: 2.336 ms
[bump] bump-render=height: FPS: 422 FrameTime: 2.370 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 323 FrameTime: 3.096 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 207 FrameTime: 4.831 ms
[pulsar] light=false:quads=5:texture=false: FPS: 399 FrameTime: 2.506 ms
[desktop] blur-radius=5:effect=blur:passes=1:separable=true:windows=4: FPS: 223 FrameTime: 4.484 ms
[desktop] effect=shadow:windows=4: FPS: 297 FrameTime: 3.367 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 312 FrameTime: 3.205 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=subdata: FPS: 308 FrameTime: 3.247 ms
[buffer] columns=200:interleave=true:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 318 FrameTime: 3.145 ms
[ideas] speed=duration: FPS: 363 FrameTime: 2.755 ms
[jellyfish] <default>: FPS: 323 FrameTime: 3.096 ms
[terrain] <default>: FPS: 76 FrameTime: 13.158 ms
[shadow] <default>: FPS: 345 FrameTime: 2.899 ms
[refract] <default>: FPS: 182 FrameTime: 5.495 ms
[conditionals] fragment-steps=0:vertex-steps=0: FPS: 355 FrameTime: 2.817 ms
[conditionals] fragment-steps=5:vertex-steps=0: FPS: 355 FrameTime: 2.817 ms
[conditionals] fragment-steps=0:vertex-steps=5: FPS: 354 FrameTime: 2.825 ms
[function] fragment-complexity=low:fragment-steps=5: FPS: 355 FrameTime: 2.817 ms
[function] fragment-complexity=medium:fragment-steps=5: FPS: 354 FrameTime: 2.825 ms
[loop] fragment-loop=false:fragment-steps=5:vertex-steps=5: FPS: 353 FrameTime: 2.833 ms
[loop] fragment-steps=5:fragment-uniform=false:vertex-steps=5: FPS: 353 FrameTime: 2.833 ms
[loop] fragment-steps=5:fragment-uniform=true:vertex-steps=5: FPS: 355 FrameTime: 2.817 ms
=======================================================
glmark2 Score: 352
=======================================================
and for AMD:
=======================================================
glmark2 2014.03+git20150611.fa71af2d
=======================================================
OpenGL Information
GL_VENDOR: X.Org
GL_RENDERER: AMD ICELAND (DRM 3.26.0, 4.18.0-21-generic, LLVM 8.0.0)
GL_VERSION: 4.5 (Compatibility Profile) Mesa 19.0.1 - padoka PPA
=======================================================
[build] use-vbo=false: FPS: 162 FrameTime: 6.173 ms
[build] use-vbo=true: FPS: 160 FrameTime: 6.250 ms
[texture] texture-filter=nearest: FPS: 160 FrameTime: 6.250 ms
[texture] texture-filter=linear: FPS: 159 FrameTime: 6.289 ms
[texture] texture-filter=mipmap: FPS: 157 FrameTime: 6.369 ms
[shading] shading=gouraud: FPS: 159 FrameTime: 6.289 ms
[shading] shading=blinn-phong-inf: FPS: 160 FrameTime: 6.250 ms
[shading] shading=phong: FPS: 161 FrameTime: 6.211 ms
[shading] shading=cel: FPS: 161 FrameTime: 6.211 ms
[bump] bump-render=high-poly: FPS: 163 FrameTime: 6.135 ms
[bump] bump-render=normals: FPS: 162 FrameTime: 6.173 ms
[bump] bump-render=height: FPS: 162 FrameTime: 6.173 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 140 FrameTime: 7.143 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 128 FrameTime: 7.812 ms
[pulsar] light=false:quads=5:texture=false: FPS: 159 FrameTime: 6.289 ms
[desktop] blur-radius=5:effect=blur:passes=1:separable=true:windows=4: FPS: 142 FrameTime: 7.042 ms
[desktop] effect=shadow:windows=4: FPS: 154 FrameTime: 6.494 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 136 FrameTime: 7.353 ms
[buffer] columns=200:interleave=false:update-dispersion=0.9:update-fraction=0.5:update-method=subdata: FPS: 130 FrameTime: 7.692 ms
[buffer] columns=200:interleave=true:update-dispersion=0.9:update-fraction=0.5:update-method=map: FPS: 136 FrameTime: 7.353 ms
[ideas] speed=duration: FPS: 152 FrameTime: 6.579 ms
[jellyfish] <default>: FPS: 156 FrameTime: 6.410 ms
[terrain] <default>: FPS: 79 FrameTime: 12.658 ms
[shadow] <default>: FPS: 152 FrameTime: 6.579 ms
[refract] <default>: FPS: 89 FrameTime: 11.236 ms
[conditionals] fragment-steps=0:vertex-steps=0: FPS: 159 FrameTime: 6.289 ms
[conditionals] fragment-steps=5:vertex-steps=0: FPS: 160 FrameTime: 6.250 ms
[conditionals] fragment-steps=0:vertex-steps=5: FPS: 159 FrameTime: 6.289 ms
[function] fragment-complexity=low:fragment-steps=5: FPS: 160 FrameTime: 6.250 ms
[function] fragment-complexity=medium:fragment-steps=5: FPS: 159 FrameTime: 6.289 ms
[loop] fragment-loop=false:fragment-steps=5:vertex-steps=5: FPS: 160 FrameTime: 6.250 ms
[loop] fragment-steps=5:fragment-uniform=false:vertex-steps=5: FPS: 160 FrameTime: 6.250 ms
[loop] fragment-steps=5:fragment-uniform=true:vertex-steps=5: FPS: 160 FrameTime: 6.250 ms
=======================================================
glmark2 Score: 150
=======================================================
To have the latest mesa I use the padoka drivers, maybe this will improve somewhat the performance and overall experience in your case too, with intel performing far better that the AMD gpu.