That's odd that it doesn't show 240hz on nvidia control panel. There is a driver to install on windows (apart from the firmware). Stupid question but thought i would mention incase you haven't installed it.So, I've finally had some time this evening to play around setting up the monitor.
Now, initially it was on firmware version 1010 and it was configured to 240Hz without any flickering whatsoever. There was an issue in Windows desktop with the brightness, I had it set to Automatic where it only activates the Backlight Array when there's HDR content. Windows HDR settings just absolutely suck at the moment, so even though I had the windows display settings to HDR content, it wasn't recognising this and was automatically lowering the brightness level. At that time, I did have the option to just the Backlight Array to permanently on in the monitor OSD, but didn't actually play around at all with it.
I wanted to get it onto the latest firmware so found the download on Samsungs website on the display page / Support / Downloads section. There's a recent update to 1013 which apparently improves HDR colours, and from what I'm reading on Reddit and other places, it's a SIGNIFICANT improvement. BUT, there are a few people saying it's reintroduced flickering when setting 240Hz with HDR.
To update, initially I tried a generic USB, it found the .img file, but failed a few times reaching 16%. So luckily I had a decent high end Samsung USB which I tried and it worked first time.
So now, brightness is far better, no flickering, still no pops from the PSU. BUT, I currently don't have 240Hz as an option other than on the Display OSD. In both the windows driver and nvidia control panel, it maxes out at 120Hz.
So still need to do some further investigation.
I'm not worried quite frankly, I'll work around it. But I can understand why a lot of people just assume it's defective. It's not very user friendly, and issues like this should be far simpler for the user without needing so much troubleshooting. Doesn't put me personally off the monitor in any way, I actually get a kick out of troubleshooting, and the benfits of the display so far far outweigh the issues I've faced.