Photoshop 26.2.0, Windows 11 24H2, ansd automatic color management

Having the same issue, the only way to have 30bit enabled in photoshop ( and working )  is only with ACM on. 

Also windows color management is not changing ICC profiles anymore. If you check/uncheck the "use my settings for this device" will not make any profle change. The only option that works is the legacy compatibility on each app, which of course is not a solution. This is by far one of the worst bug in Microsoft for Professional Designers/Photographers/Visual Artists.

The  advice is to disable ACM and allow Adobe and other professional software to handle color accurately just like they'have been doing for last 20 years.

The ACM is still broken and there is a wide range of weird issues with it.

The explanation here applies to  SDR only. With  HDR on it's more confusing.

Basically the idea of ACM is, any legacy (non windows UI app) are considered to only run in sRGB mode and they always deem your display as a sRGB narrow gamut display. The biggest issue with this is, there are quite many apps including Photoshop that knows how to handle wide gamut for decades and now they lose the capability. Even Chrome and Edge have been doing this well that all contents (including the UI) are not oversaturated and are converted accordingly per your display profile. They have been able  to show wide  gamut contents (P3, AdobeRGB, proPhoto) correctly before ACM. But now with ACM they are fully restricted to sRGB. Check "wide Gamut test" pages for yourself.

And Photoshop, as a legacy app, will be wide-gamut blind after enabling ACM. One workaround is to check "use lecacy ICC " in the app setting. It will override ACM (so you notice the banners  and UI elements are oversatureated again with ACM). But I am pretty sure the color conversion is done wrong in this way.  Pictures become washed away and less saturated than they should be. It looks like the color conversion is done "twice"!  Everything appeared wrong in this case.

The last thing is, we don't know under ACM if Windows handled the conversion correctly. Ideally it should use your stored ICC profile that has the measured XYZ coordinates to force everything from display native gamut to sRGB, right? But it might have used the EDID instead, which are factory preset XYZ coordinates that are never accurate. 

Windows have been disastrous on color management. They thought they are clever by introducing ACM but instead they just created another more sophisticated CRXP .

@bobkn 

1 - there is no such thing as "enabling automatic color management" in Photoshop. Color management is always running. The question is just whether there is an embedded document profile and a valid monitor profile.

2 - color management and bit depth are two different things unrelated to each other. One does not affect the other.

3 - 10 bit output needs to be enabled in the Nvidia driver. As far as I know it's only available with the Studio driver, it is not available with the Game Ready driver. You also need to connect the monitor by DisplayPort. Once enabled in the driver, it can be set in Photoshop Preferences > Performance.

4 - it is very easy to confirm whether the display really is running at 10 bit per channel depth (30 bit). Just make a gradient in Photoshop, in a 16 bit document. Almost any gradient will do. If you see any banding there, any stepping between values, you do not have a 10 display pipeline. True 10 bit display is perfectly smooth in every possible instance.