Then obviously 2018, Oct~Dec has asicboost. To "bring dying boards", then perhaps Braiins OS with options to disable failing sensors, or carefully adjust your speed and voltage to find the optimum values. bOS is currently S9 to S9i, nothing newer, no hydros, no T9s or R4s etc at least until after they finish replacing cgminer with bosminer next year when they will start adding units like the S17, etc.
The other firmwares have dev fees, and you don't want that anyway, no matter what bells and whistles they promise.
Also cleaning the boards often bring them back to life, don't ask why, but I have seen it. Wash them with water and soap and leave them to dry, (output from another miner works great as dryer) just like that some magically return to life...
A update with postive results!
Thanks for all of your replies to my threads. I used the Dec 2018 bitmain firmware to bring 6 S9s back to life that wouldnt come online. In addition, a 7th would run for a day and then get into a uncrecoverable crash, while still powered on... I am runnin gin LPM and LP enhancement and it seems to be running stable. A 8th would read 160 degreesc and cause all mining to stop so I am running that in LPM as well, and it seems to work well.
Thanks for the help everyone.