Photoshop 2025 v26.5 was working absolutely fine, then I made the mistake of updating to the latest patch, version 26.6.0 on my M4 Mac Mini.
After updating to 26.6, the actual document window is solid black - even if I open a photo or previous document...

Even though the Layers and Channels palette preview thumbnails are showing what's in the document...

After digging around in Preferences, I tried turning off the "Use Graphics Processing" option and relaunching Photoshop afterwards, and it's working fine again...

I'm just wondering if this is a bug related to the M4 Mac Mini graphics driver compatibility with the version 26.6.0 release? And, if so, when can we expect a fix from Adobe.
I've discovered the workaround for now, but obviously turning off the Graphics Processing setting will affect perfomance. Like I say, with this option switched on previously to the latest 26.6.0 release, it was working fine so it must be a new bug with 26.6.
I'm never updating this software ever again!!