By replacing a bunch of strupper_m function calls in source3/nmbd/ with strlower_m I was able to get /usr/bin/nmblookup to output 'lowercase' netbios and workgroup names.
By replacing a bunch of strupper_m function calls in source3/nmbd/ with strlower_m I was able to get /usr/bin/nmblookup to output 'lowercase' netbios and workgroup names.