When I checked my mailbox yesterday, along with a pile of catalogs and announcements were multiple notices of attempted delivery from UPS and Chronopost (which appears to be how packages sent USPS Priority Express International get delivered here).
I went online to both services, added info as needed (e.g., new phone number !), and made plans to hang out in the apartment until the deliveries arrived.
Which was just now: Both were delivered within 5 minutes of each other, near 10:30.
Next steps: Check the tracking information for the remaining two packages presumably coming via Chronopost (Done, rescheduled for Monday). And find out if there’s a way to get Customs to refund the fees that shouldn’t have been charged because the Certificat de Changement de Residence was included with all the packages I sent.