I shoot primarily with lenses that do not identify themselves to the camera. My solution has been to edit the EXIF data after the fact using
ExifTool by Phil Harvey. Although the basic tool has a non-graphical interface and uses the command line, a graphical user interface is available (
LINK). With ExifTool you can edit pretty much the entire metadata set that may be embedded in the image file. I regularly use it to input lens data and, for film scans, camera and date info as well.
In terms of work flow, it is easiest to do the ExifTool work before the import into Lightroom, though not impossible to do it afterwards. I would suggest downloading both ExifTool and ExifToolGUI (you need both to get the graphical interface) and playing with it until you are comfortable with what it can do.
Steve
P.S. Many thanks to tuco for putting me on to this tool a couple of years back.