Is there a key combination that shuts down a Mac Studio?

Control-F2 to select the Apple menu (may require the fn key to get real F2). Apple is highlighted.

... then DownArrow enough times to select Shutdown off that menu (about seven times, depending on MacOS version). each section is highlighted as you press DownArrow.

I had the same issue and found this as a solution - go to System Preferences > Keyboard under the tab Shortcuts and select App Shortcuts in the left column, then click the plus button. In the dialog box use Sleep (or the equivalent to your "Sleep" in your OS language - just check the Apple menu item) for the "Menu Title" field and select a free shortcut. I used F6 using the ‘moon’ as I do not use ‘do not disturb’. You will then find it is listed under the  menu.

We never shutdown any of our Mac's and none have ever prematurely failed from being on 24-7.

Our Intel Mac's are setup to Sleep Display after 10 minutes and the Computer Sleeps when they are not in use. They never get Shutdown and only get restarted for updates or troubleshooting.

Our M1 Mac is setup to Sleep (turn off) Display after 10 minutes and Computer Sleep is Disabled. It never get Shutdown and only get restarted for updates or troubleshooting.

FWIW the new M1 Mac's consume far less power in standby mode than Intel Mac's. I also believe that excessive powering off/on puts more strain on the hardware, then just leaving a Mac on 24-7 in standby mode.

The only reason I can think of to shutdown, is if your local power grid is flaky or in a severe thunderstorm and then it should be disconnected from the power and ethernet until the storm passes.

Control-Power or Control-MediaEject is supposed to put up this dialog box:

Shutdown is highlighted as the default, so pressing Return takes the default.

I believe the first letter of any others chooses them and ESC abandons the entire business.

(the aqua color in the highlight gives you an idea of how long ago I captured this screenshot)