手のひらツールのショートカット

とりあえず環境設定のリセットはしてください。

https://helpx.adobe.com/jp/illustrator/using/setting-preferences.html

OSの上書きアップグレードやIllustratorで環境を引き継いでのアップグレードをした場合はとブルが起きやすい傾向があります。

Hi there,

Sorry to hear about your experience. There has been no change in keyboard shortcuts in Adobe Illustrator CC2020. Please check if there is any other app that may be interfering with keyboard shortcuts. You may take help from Apple support article https://support.apple.com/en-in/guide/mac-help/mchlp2864/mac

I'd recommend updating Illustrator to the latest version. Also, you may try resetting the preferences of Adobe Illustrator once. Please follow the instructions below to do that:

• Close all Adobe applications. 
• Go to locations 
• ~/Library/Caches 
• ~/Library/Application Support/Adobe 
• ~/Library/Preferences 
• Rename Adobe Illustrator, com.adobe.illustrator and Adobe Illustrator 24 Settings folders to Adobe Illustrator.old, com.adobe.illustrator.old and Adobe Illustrator 24 Settings.old 
• Launch Illustrator from the Creative Cloud. 

**Please note that resetting preferences will remove all the custom settings and Illustrator will launch with default settings. This way all your old settings will be saved in .old folders and Illustrator will recreate new folders with default settings. 

Let us know if it helps you out. Looking forward to your response.

Regards,

Ashutosh