Hi @Iantaylor2050 ,
From your information, I think you want to filter the results inside a people picker.
If my understand is correct, currently, there is no directly way to achieve this. When applying a Filter action to the People Picker ComboBox(Choices([@DataSourcename].Peoplepick)), the People Picker ComboBox would not show up any results.
As a workaround, we can use Office 365 Users connection to achieve this. I did a test on my side for your reference.
1. Add the Office 365 Users connection.
2. Unlock the People Picker field DataCard in the Edit form, set the Items property of the People Picker ComboBox to following:
Filter(Office365Users.SearchUser({searchTerm: DataCardValue6.SearchText, top:999}),EndsWith(Mail, "@abc.com"))

Note: The top property within the Office365Users.SearchUser() could limit the returned user results, the Maximum value is 999, in other words, you could only return 999 users at most from your org once time.
3. Set the Update property of the People field DataCard in the Edit form to following:
{
Claims: "i:0#.f|membership|" & Lower(DataCardValue6.Selected.Mail),
DisplayName: DataCardValue6.Selected.DisplayName,
Email: DataCardValue6.Selected.Mail,
Department: "",
JobTitle: "",
Picture: ""
}

Check result this time.
Best regards,
Allen