Note: You will need to loop through all the potential pages using this method. You may also use an aggregate like most of the other examples and match _t:Person for all the people. This includes the attendees (not the attendees card information though as that is stored on type Attendee - visitor management).
This is baisically showing the GetPeopleAsync Call.
Example in C#
var personInfo = await client.GetPeopleAsync(FolderInfo folder, 0, 1000)
Example in CURL
curl -X GET \
'https://keepapi.feenicshosting.com/api/f/INSTANCE.KEY/people?page=0&pageSize=1000' \
-H 'Authorization: Bearer TOKEN_GOES_HERE'