If you want to make chicken parmesan without breadcrumbs, there are a few options.
Make a naked chicken parm by simply leaving the breadcrumbs off the dish. Baked chicken covered in tomato sauce and melted cheese is really delicious with or without the breadcrumbs.
For a gluten-free breading, look for gluten-free breadcrumbs or swap in almond meal to add a nutty crust to the chicken.
For low-carb breading, many people use crushed pork rinds or simply bread the chicken in grated Parmesan cheese.