You can use the option in Moodle to submit in groups but require only one group submission. When the grader grades, all of the group members can receive the same grade as the one group submission and the feedback file
#1 In the Assignment settings, scroll down to Group submission settings
#2 Next scroll down to Common module settings
#3 The grader can just select the group and View all submission
#4 Then they select just one of the group submissions to grade (not showing student name to select to the left of the red checkmark)
#5 Follow the steps below to Give the same feedback file to multiple students
Note: in step 4, the grader may select just one group or one student at a time.
The above is a screenshot from this page in Moodle Docs https://docs.moodle.org/36/en/Using_Assignment#Downloading_student_submissions )