This shortcut should still be working. Did you check that it was correctly set up in the settings ? (click on your username on the top-right corner, select "system settings" then "keyboard", switch to "shortcuts" tab and select "system" section, there you will be able to configure the keyboard shortcut for the "run command" prompt)
This shortcut should still be working. Did you check that it was correctly set up in the settings ? (click on your username on the top-right corner, select "system settings" then "keyboard", switch to "shortcuts" tab and select "system" section, there you will be able to configure the keyboard shortcut for the "run command" prompt)