It’s the other way around. Flock is the subprocessor for whoever hired them to collect data. If they are collecting data on behalf a city or municipality, those are the entities you need to address.
I'm not sure about that, I'm pretty sure any company that has your PII is obliged to follow the law, regardless of their contracts with their customers/vendors. Law doesn't make you investigate who's the end customer for your data, only who has it.
As for "subprocessor" -- it might as well be the case that both sides are subprocessors for each other, nothing wrong with that.
I'm not sure about that, I'm pretty sure any company that has your PII is obliged to follow the law, regardless of their contracts with their customers/vendors. Law doesn't make you investigate who's the end customer for your data, only who has it.
As for "subprocessor" -- it might as well be the case that both sides are subprocessors for each other, nothing wrong with that.