Ralliart can't be considered a tuner, it was literally the Mitsubishi rally/Dakar division. Yes, it was estabilished by Cowan but then it almost immediately became the official Mitsubishi works team, so in my view it can't be considered a tuner.

The line is often blurred between works/semi-works/private effort. Prodrive, M-Sport, MSD were all tuners that were chosen by manufacturers to run their WRC program, so to me they're works team too, just not in-house. M-Sport from 2013 on, after Ford officially left, I consider a semi-works "tuner".
Then we have Kronos Citroen in 2006 or PH-Sport Citroen in 2016 or Jolly Club Lancia (especially in 1992 and 1993 when there was no official works Lancia team) are semi-works tuners to me, but they're just using the old works cars.

Maybe Prodrive with Porsche and BMW M3 in the late 80's? I don't know if those were more Prodrive tuner projects or with actual manufacturer backing.