Some people's Office 2021 may have a new look, and some may not have received an update. Let's share how to force the new UI. Create a new text file, copy and paste the code below into the text file, change the file extension to .reg, and run it to add it to the registry.
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides]
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\access]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\excel]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\onenote]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\outlook]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\powerpoint]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\project]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\publisher]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\visio]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\word]
"Microsoft.Office.UXPlatform.FluentSVRefresh"="true"
"Microsoft.Office.UXPlatform.RibbonTouchOptimization"="true"
"Microsoft.Office.UXPlatform.FluentSVRibbonOptionsMenu"="true"
