For Blender 2.8, the real-time displaying of an objects wireframe in the 3D View is different than off-line rendering a wireframe or outline. Whilst the first aids meshing, being able to see structure and density at a glance whilst working, the latter can be used to make finished images look like they were rendered in SketchUp. This is done using Blender 2.8’s Freestyle rendering option.
Scene/Object Set up
To render outlines make sure at the very least any object to be rendered has at least a basic Material assigned with a Diffuse colour set, with the Scene appropriately lit. As outlines are a rendering process a Camera entity is needed, positioned relative to the point of view expected of final image output.
Design note: rendering outlines does not specifically require complex  node-based materials , a simple Material assignment with an (optional) Diffuse colour will suffice (all materials have a off-white diffuse colour set and used by default that can be changed in the Node Editor (show in Shading Workspace  below) or in Material Properties ).
Rendering and outline around objects is independent of materials but objects should have at least a basic Material assigned to be able to control some aspects of the final render, Diffuse colour in particular
To produce a SketchUp style render, once a Scene and objects are prepped, in Render Properties  click the checkbox next to Freestyle  enabling access to a set of basic options (click the arrow to expand). Here the initial width of the outline can be set changing Line Thickness (1.000 px being the default, Line Thickness: 1.000 px).
With Freestyle now enabled, to render the basic outline press F12, which then displays the render window (pop-up), and/or switch to the Rendering Workspace to see the results.
With the scene set up and Freestyle enabled press F12 to initialise rendering and see the basic result, an outline (black by default) around all objects in the scene (using a simplified, object intersection, occlusion).
For more control over rendered outlines a set of additional options are available to change the appearance of the line. At it’s most basic the Freestyle options available in View Layer Properties allow the outlines colour to be changed under Freestyle Line Style . Here accessing the Color properties panel an option to change the lines Base Color  can be selected and set (colour-wheel selection).
Design note: the properties and options available allow for far more sophisticated line work to be rendered from the basics discussed above.
Old *.blend files
As a consequence of changes to Blender 2.8’s rendering and material systems loading old or legacy *.blend files set up to produce SketchUp style outlined renders initially won’t work – all the settings and options included in the file will likely be available but not necessarily updated for use in Blender 2.8. In this situation what’s likely missing is a Freestyle Line Set, the datablock that holds all the attributes of an given outline.
Design note: when loading old *.blend files disable Load UI in Open Blender File settings bottom-left to utilise Blender 2.8’s interface – for truly old files, pre Blender 2.49, loading legacy interface data may cause issues so it’s preferably to disable this information.
Access View Layer Properties  and in the Freestyle Line Set subsection  click the + (plus) button  to the right of the lineset aperture. A new entry will appear, titled LineSet by default, accompanied by a new group of settings and options below, pressing F12 now will include a basic outline in the render per the properties set/used.
Design note: LineSet functions in a similar way to materials in that a Material acts as a container of sorts for associated options and settings.
For legacy SketchUp style rendering projects it’s likely the LineSet property  is not available/has not been created  resulting in no outline during rendering. Add one, click the + button , to generate an outline.
Walkthrough showing how to render a basic SketchUp style outline render in Blender 2.8