Using Classic Outlook on Windows for personal email, calendar, and contact management
For anyone that is a sysadmin and working on domain, use the latest Office 2021/2019/2016 ADMX to prevent the updates from pushing to your users.
I am pushing it to machines instead of user accounts, so I navigate to the following:
Computer Configuration -> Policies -> Administrative Templates -> Microsoft Office 2016 (Machine) -> Updates -> Prevent Office from being updated to a specific version
Enable the policy, enter 16.0.17231.20182:16.0.17126.20132|16.0.17231.20194:16.0.17126.20132
Proceed to save and push policy out to users.