the other option is 3utools, but unfortunately that requires windows as well.
with 3utools you can simply perform a anti-recovery flash which installs the latest IOS and firmware. it will wipe the passcode out. it will also wipe out any data on the phone, but it sounds like that's a non-issue. and since there is no icloud, it will make the phone truly OOTB/factory-fresh, ready to be set up.
3utools is free and it's a legit utility. maybe you have a friend who will install it in order to perform the flash if your iphone.
good luck