So that does not apply for 2015 or 2016 bikes?
The Consent Decree does not require Harley to void the warranty on 2015 or 2016 models, no. It is specific in its years, it covers 2017 - 2020. Now, Harley already has wording in its warranty that says that if you put the bike into a state that causes it to be illegal to operate on the roadways of the territory it's registered in, then they can void the warranty for that purpose; they also say that if you put on parts designed to increase performance, that is a warranty-voiding event, so you could argue that yes, all these things can void the warranty. Also, if you put a trailer hitch on, your warranty is voided.
Now, the point here is that this wording has been in Harley's warranty for years and years and years, yet we don't hear a lot about people whose warranty was voided for putting on an air cleaner. So you probably don't have much to worry about, unless you're doing something radical like a turbo.
However, Harley's quite strict about the trailer hitch thing; I found a thread on HDForums going back over 9 years ago where people were complaining because Harley saw a trailer hitch on their bike and voided the warranty.
I haven't bought a tuner because I assumed it impacted all bikes still under factory or extended warranties. I purchased my 2016 as NOS, with the warranty period starting on April 1 of 2017. That leaves just over a year remaining on the warranty. Plan A was to wait until April 2 of 2018 to install an FP3 and air intake.
Okay, so -- technically, that would probably be grounds to void the warranty, but it does not mean that they WILL void the warranty. Especially if you go with an EPA-legal air intake, you'll probably be fine. But only probably; you really should ask your dealer what they think about that scenario.
Plan B was to get the genuine H-D turner. Others have noted that the FP3 provides some benefits for bikes with stock intakes and exhaust. Can the same be said for the H-D tuner?
The H-D tuner does no good to a stock bike. It can only be used when you have at least a Stage I (intake & exhaust upgrade). The FP3, as a product, is way better than the HD tuner (I know, I have had both). If you get an intake and exhaust, the H-D tuner should be able to handle it and keep everything EPA-compliant and street legal. But you won't get the goodies that the FP3 has, like the readouts of all the temperatures and MPG and voltmeter and all the other things the FP3 does.
It's all a gamble. You may never have a problem; I had my Street 750 for 2 years, never had even the slightest hint of repair needs. But Inky750 and TusconMax1 have had endless problems with theirs. I think Max was running the FP3 and never had warranty problems at his dealer, so maybe it's okay for pre-2017 bikes, or maybe his dealer just didn't care to rat him out. Again, you should consult with your dealer as to what they think.
That's not an option for those of us with 2017 - 2021 bikes. The dealer has no say, Harley automatically immediately voids the powertrain warranty on any 2017-2021 model that's been tuned with an aftermarket tuner, no choice about it.