Get a phone number in an area code far away from where you live, but where there aren't too many overlapping prefixes so you can recognize them quickly.
Then any "local" call is likely to be spam. Filter as needed with a rule matching this areacode.
I did this by moving across the country. Anytime I get a call that is "local" to my phone number, I know it is not for me. (sometimes spam, sometimes misdial, never someone I know (I have all their numbers in my phone already)).
Anytime I get a call that is local to my actual location, it's almost always someone who has a legitimate need to get a hold of me (or my ISP trying to upsell me to landline phone)
Then any "local" call is likely to be spam. Filter as needed with a rule matching this areacode.