@bizziboi I'm using it only in a "wired" setup (haven't even tried wireless... I did even know that wireless is an option for OSX, considering that even getting it recognised in a "wired" setup required 3rd-party drivers... cause well, yeah, OSX...).
Other than that: Yes, I'm also using OSX. I tried it on two different versions actually (two different Macbook Airs), the one I'm currently on is running OSX Catalina 10.15 and the other one is running the latest Mojave version (I believe, 10.14.6... I don't have it at hand right now). Both were working fine days ago, my wife and I have been playing DS and DST on these notebooks for over a year with the exact same controllers and setup.
As an additional note: I have the latest 360Controller driver installed on my setup (the Catalina one) https://github.com/360Controller/360Controller/releases (a year ago, Steam alone would not recognise the controller so I had to use this 3rd-party driver in order to get it working - perhaps that's no longer needed now, but I have not tried using the controller without it); I installed the latest Alpha release yesterday just to see whether that makes a difference or not... it did not. My wife's notebook has the latest stable version installed (0.16.11). Steam in Big Picture mode recognises the controller for both of us and we can navigate the Steam menus just fine with it, but in DST (I have not tried DS actually, but I can take a look there too) doesn't seem to want to process the inputs.
One additional hint that might be of help: although the controller inputs are totally ignored in DST, when the game loads, it does seem to recognise that a controller is connected. The reason I'm saying that is because the navigation hints (if that's what you would even call them) on the main screen and menus are controller specific (these the little icons that show up telling you to press A to select the given option or Y, etc.). So somehow, on init, the game was able to determine that there's a controller connected, but that's as far as it goes... it then fails to actually read the controller inputs and in the game's Options, Keyboard/Mouse is the only input device type that is allowed for selection (the "right arrow" is enabled so I could in theory select another input device type, but pressing on it does nothing... at most, the screen seems to flicker for a second but Keyboard/Mouse is always the only selectable option).
I'll delete the client.ini and the client_save as you suggested and I'll come back with some feedback.