VinnyBlood’s method can work,but if you just want to get the texture manually somtimes but not every frame,see about this.
lets go in code.
GetGameViewport()->GetRenderTargetTexture will return the member RenderTargetTextureRHI in client,SceneViewport.UseSeparateRenderTarget() decide whether the RenderTargetTextureRHI is valid or not(FSceneViewport::InitDynamicRHI),wo if you want the texture,you gonna to make SceneViewport.bUseSeparateRenderTarget ture.if this flag value set as false,render result will send to the backbuffer directly.And this value setted in construct function with ViewportWidget(SWiewport) member parameter.
and as a violent way you can simply set GameViewportWidgetRef’s construct paramater RenderDirectlyToWindows to false in UGameEngine::CreateGameViewportWidget(),and every thing about this will be same with the editor.
However,you couldnt access to viewport dynamicrhi(just like editor),and you will get a upset down viewport in android.