Just got our acceptance email today, in total it took about 7 weeks (assuming the return priority mail is on time).
Passport book renewal, regular processing, didn't go through any special contact channels after mailing:

3/06/21 - Mailed from CT (USPS Priority Mail) to Philadelphia, PA processing center
4/05/21 - Got email notification from State Dept for "in-process"
4/06/21 - Check cashed
4/19/21 - Got email notification for "approved", second email ~2 hours later for "shipped" with tracking number
4/25/21 - Estimated delivery date