I’m quite certain that you need to sign up via healthcare.gov (or your state’s own ACA exchange, if it has one) in order to receive the an ACA premium tax credit subsidy. Yes, a broker can set it up for you, but they too need to do it via the exchange.
An individual purchasing directly from an insurance company cannot take advantage of the subsidy.
After quickly looking at the Floridablue website, it appears that they have created an integrated experience that allows you to start on their website and then it will display the healthcare.gov site for part of the application process, then return to Florida blue to complete the process. I guess that’s, ok. But be sure about it. If you aren’t properly registered on healthcare.gov, you won’t get the subsidy now or at tax time.