I was there fairly recently. 2019 or 2020 maybe. Didn’t turn up anything in a few really nice looking spots, so the next few nice looking holes or runs I just waded right through the middle without fishing them, to see if I kicked any fish out. I didn’t.
Got up to the above mentioned trib, and noticed the precipitate line at the confluence and figured one was the problem, and one was probably ok, and chose to gamble and go up the trib. Immediately started catching wild Browns, and good numbers of them. Was a head scratcher, as I was expecting to find Brookies, if anything. The precipitate line at the confluence, and the presence of Browns in the trib, but not finding anything, even Brookies in Mill, suggest the main stem of Mill still has some serious issues.
Edit: I was above the confluence with Wolf Creek, FWIW. Maybe there’s some further tempering of the water as it moved downstream and picks up more tribs.