I installed new 2017+ 86 headlights on my FR-S last month because my old Winjets had become yellow and scratched. I did not need any special brackets.
However, I ran into a couple of issues, one of which I still need to correct.
I made the mistake of buying a 6pin/8pin adapter from eBay that claimed to be plug-and-play for 86 headlights on the FR-S:
https://www.ebay.com/itm/234974462311 Do NOT buy this unless you want headaches.
The truth was that the DRLs would only come on if side-indicator / parking lights were on and NOT if you took the car out of park without any other lights on. On the adapter I bought, it was just sending power from the side-indicator / parking light wire from the turn signal connector to the DRL.
Remember that on the FR-S the factory headlight uses a single bulb for both DRL and high beam. It just sends less power to the bulb when in DRL mode than in high-beam mode.
I modified the adapter so that the DRL and high beam pins on the 8pin connector would get power from the same DRL / High beam wire from the FR-S' 4 pin headlight connector.
In DRL-mode, just the DRLs come on. In high-beam mode, both come on. I'm not sure if that's consistent with how the 86 behaves (probably not), but it's better than before. I admit that I never bothered to check what voltage the DRLs on the new headlights require. It's entirely possible that the FR-S is going to send too much and burn-out the LEDs, especially if I leave the high-beams on too long.
So there's just one more problem left. My fog lights don't work anymore. I didn't realize it and didn't think to inspect all of the wires on the adapter and test the fogs until after I had put the bumper back on. The issue is that if you have the OEM fog lights, those lights share a common 4-pin connector with the turn signal light just above it. The adapter did not pass-through the fog-light wire.
To fix the fogs, I *think* I might be able to get enough access to the adapter to make modifications via the wheel well liner behind the bumper so I won't have to take the bumper off again, but I've been too lazy to try. It's something that might wait until just before I have to get an inspection sticker next year.