Yes, for full resolution@60Hz you need the Usb-c/Thunderbolt or Displayport connections. HMDI only manages 30 Hz with 5120x2160 - so the HDMI connections are relatively useless - unless you want to connect a Playstation or something in between and enjoy black bars left and right. Or for Picture-In-Picture or two PCs side by side.

Yes, can be set in the monitor setting (incl. pressing the Option or Command key).

Yes, works fine with my M3 air

Mine runs on an MB Pro, M1, 64GB RAM. Maximum resolution and colour depth without any problems. The image signal goes to the monitor via the USP-C PD cable and the MB is supplied with power. So compare the graphics performance of the corresponding Mac Studio with the MB Pro M1, just as a tip.

The desired model has already been sent to us under this link. Dell U4025QW (5120 x 2160 pixels, 40") However, it is not yet available.

Among the TV wall mounts there are some that should fit the screen. Simply enter a minimum weight of 14kg and VESA 100x100 in the filter and select. You may need to ensure that the dimensions are not larger than the monitor itself.

I use the DP and USB3 ports with my desktop and only use the Thunderbolt port with the laptop so I can use the inbuilt hub/KVM switch.

Using the Macbook in conjunction with the monitor is extremely problematic. Only twice was it possible to establish a connection, but each time this was interrupted when the Macbook was disconnected. A firmware update brought no improvement. During the short connection phases, the picture was displayed in normal resolution. In addition, the software required to manage the monitor causes difficulties: It crashes repeatedly on the Mac OS operating system and causes unstable system performance on Windows. Therefore, this monitor is not recommended for use with Mac OS.

39.2 cm high and 92.5 cm wide.

My desk is 80cm deep and I'm fine with the size.

I use the Dell U4021QW as a second monitor on a Mac Book Pro 16" with M1max, connected via the supplied Thunderbolt4 cable. I have connected Ethernet and USB-A sticks to the monitor. This works with full 5K resolution and the Mac is also supplied with power perfectly. I don't know how long the connection cable should be, but it is important that it is a Thunderbolt 4 cable (i.e. not just a USB-C cable, which has the same connectors). A small disadvantage with MacOS 12: If you put the Mac into hibernation mode, all open windows are on the main screen (the one with the menu bar) when you wake up again - a bit annoying and that's why I always switch off the Mac, then all open windows are displayed again where they were. I haven't tried out in detail how this works with MacOS 13 Ventura and the new Stage Manager. There are some settings that might solve the problem. Basically, I am very satisfied with the monitor. I really appreciate the "curved" and the Ethernet connection in the monitor. The Apple Studio Display doesn't have either of these. The Dell has an anti-reflective, slightly matt display (similar to the Studio Display with nano-coating). I find that great for working. However, if you want to watch films, a glossy display, like the normal Studio Display, would be a little sharper / clearer / more brilliant.

That was probably not meant as a question? I've had the monitor for almost 1 year now. Picture is very good, have it at about 40% brightness, so it should be bright enough for most people. The curvature of the display is nice. The integrated docking station also works quite ok. If you only have 1 device to connect to, you don't need this monitor.

Yes, it can be attached to a monitor arm. I have adjusted the filters here, all the monitor brackets shown fit the monitor: https://www.digitec.ch/de/s1/producttype/monitor-halterung-1986?filter=t_8289%3D178142%2Cn_11853%3D1%2Cnr_20160%3D1.0160000000000002%3A2.8448000000000007%2Cnr_2940%3D14000%3A250000%2Ct_841%3D402%2Ct_21986%3D691867&ic=monitor+bracket

Hello, probably in Displayport on both sides. but I'm not sure I'm not on Mac

The problem is the graphics card of the small MBP. Here you only have an Intel IRIS 655, which supports max. Displayport 1.2 for video output and not 1.4, which you need for the Dell. Someone has explained it in more detail here: https://www.dell.com/community/Monitors/U4021QW-2019-MacBook-Pro13-how-to-get-5120x2160-60Hz/td-p/7978567 The maximum resolution is only possible if the display can receive two DP 1.2 signals from the MacBook instead of the required 1.4. Dell may still have a current firmware that allows this, but probably not.

When I ordered the monitor (2 weeks ago), the delivery time was 2-3 days. I received the monitor within this time.

With this resolution, you have to rely on Thunderbolt anyway. HDMI simply can't handle the 5k2k resolution and 60hz. I doubt whether your Apple device can output the image with 2x Max resolution. I run two of these monitors on a Dell XPS via 2x Thunderbolt and it manages the max resolution at 2x 60hz. My Microsoft Surface Pro can do the same. I wouldn't be so sure about Apple...

No, this monitor does not have HDR and does not support VRR (Variable Refresh). However, it has 10bit colours. See the manual: https://dl.dell.com/content/manual32849407-dell-u4021qw-monitor-bedienungsanleitung.pdf?language=de-de

I have sent an enquiry.

Experience shows that questions about experience are rated most frequently when they are asked in discussions, as discussions appeal to many more customers than product questions.

The iGPU can do DP 1.2, which is enough for a maximum of 5120x2160@30Hz. And the monitor must be connected to the Thunderbolt port. DP 1.4 is only supported from the next higher Intel 11th gen CPU, which then supports up to 8K. 30Hz is usually sufficient for office use, it may be jerky when scrolling, but it is definitely unsuitable for gaming. 60Hz would be ideal.

The monitor has a bit much ports :-) It has one USB-C/Thunderbolt that delivers 90Watts and a second USB-C that delivers a maximum of 15Watts (for mobile phone, etc). Here's the overview on page 11. https://downloads.dell.com/manuals/all-products/esuprt_electronics_accessories/esuprt_electronics_accessories_monitors/dell-u4021qw-monitor_user%27s-guide_en-us.pdf

Unfortunately, it won't be adapted. You can't reach the full resolution of the monitor with this configuration. ):