Pretty easy.
The other day I was pixel peeping, at 100% magnification, images from the Leitz 35mm f/3.5 Summaron RF taken on Kodak Ektar 100 film. These would make 48″ x 72″ prints. Two things are obvious. There is minor red fringing chromatic aberration, easily removed with one click in the LRc Develop module. And while this image, taken at the lens’s sweet spot of f/8 will easily make a 13″ x 19″ print, start cropping and the definition is not quite there. Given that this is the least expensive Leitz branded 35mm lens you can buy (other than the poor earlier 35mm f/3.5 Elmar in LTM) and realizing it was first sold some 70 years ago, I’m not grumbling. But can we get a quart out of this pint pot?

1/250th, f/8, Kodak Ektar 100, Noritsu HQ scan.
Reading up on various sharpening applications I came across one named Gigapixel from Topaz labs, a long time maker of LR plug-ins. They offer 20 full trial attempts and place no watermark on the enhanced image. Nice. The cost is $100. The examples on their web site are startling, showing massive improvement in micro-contrast and detail. Using the above image I could not remotely get comparable improvement. Indeed, if there was any improvement I was very hard pressed to see it. Either Topaz Labs is using an especially ‘friendly’ image which supports their technology or this is pure snake oil. Either way, $100 saved.
Next I took a look at Affinity Photo 2, v.2.6.0, using their Develop Persona and Document->Resize Document, quadrupling the displayed pixel count, for a file which accordingly grew to four times the size:

The Document dialog in Affinity Photo 2.
Again, I could barely notice any difference compared with the original. Pass. Lots of disc space saved.
Next I tried LRc’s native controls. In the Develop module I went to Photo->Enhance where, for JPGs like this, there is only one active option named Super Resolution:

Super Resolution in LRc.
Well, the file size again quadrupled but the difference was again negligible.
Hmmm, none of this works.
Then I recalled that LRc has a simple Sharpen slider in the Develop module, one which I had not looked at in years as I was using good lenses with large digital sensors, no sharpening needed.

Optimal sharpen settings.
Now I really started seeing improvements. In the Develop module you can see ‘Before’ and ‘After’ images by hitting the ‘Y’ key, and here they are, at 100% magnification. Again, that translates to a 48″ x 72″ print:

100% pixel peeping, ‘Before’ (left) and ‘After’.
Click the image for a large original.
Look at the detail in the flag and in the fluting of the Grecian columns. A very significant improvement. Now I am not about to make prints that large but now I know I can crop images from this ancient optic and get great prints from the crops. Not half bad for an ancient bit of bottle!