The Summar, as everyone here that has one knows, is a lens that has a "signature" look, which is soft and sharp and lower contrast. Very nice for some types of photography.
What is wanted in an enlarger lens is a lens that is as perfect as possible, without a signature look...so as to not add its look to the look of the taking lens. An enlarger lens should ideally transmit "exactly" what is on the negative without changes.
In the early years of 35mm photography, (1930's) it was a selling point to Leica to indicate that the 50mm Elmar could also be used as an enlarger lens. The Elmar comes closer to being a suitable enlarger lens, as it is close to a tessar design. However, even it will not give as good a result as a purpose built enlarger lens. The reason is that camera lenses are optimized for maximum sharpness at distances close to infinity. Enlarger lenses are maximized in sharpness for distances close up, such as the distance from the lens to the easel.
The Summar would be my LAST choice to use as an enlarger lens, due to its undercorrected distortions.