How normal does a breast look after lumpectomy?

Very normal. Most skilled surgeons are able to remove "lumps" without deforming the shape of the breast. Unless large amounts of tissue are removed, or the lump is very close to the breast skin surface deformities are rare.
Fairly close to norm. Unless you are a keloid former and the area does not get infected then most incisions placed in the correct cosmetic skin lines will barely show 4 months later inside the surgeon also has to be careful to orient the dissection lines, in the breast itself , radially so we can close the dead space and maintain the normal contour - we have tricks for tissue transfer- easy for upper outer breast.
Oncoplastics. Oncoplastic surgery is the buzz word for employing plastic surgical techniques to oncologic/cancer surgery to maintain or even improve the size, shape, and hang of the breasts.