Dryer lint is likely to be plastic particles rather than natural fibers, depending on the materials you’re washing. You may not want to use it indoors or to prepare coals for cooking.
I tried drier lint. My issue was that it smelled _horrible_ as it burned. I doubt this matters very much for the food, since the starter is long gone by the time you start cooking, but I just don't want to be around it. Newspaper/brown packing paper is plenty cheap and available for me.