Several G Suite apps have a setting for G Suite admins to enable/disable the warning, like Hangouts
From Hangouts settings
Hangouts out of domain warning
By enabling this setting, you provide a warning to users when they’re
having a Hangout with users of an external domain. As an
administrator, this also provides you with more visibility into ...
I had a situation to randomly pick M or F in a column. I used this formula in Google Sheets:
=IF(RANDBETWEEN(1,2) = 1,"M","F")
Crude way, certainly not for long lists, but it works if your set of values is small.