Does "ALTER TABLE ONLY parent" work correctly? Namely, do not affect existing partitions, but cause future partitions to acquire the new setting.
This sounds very much related to previous discussion on REPLICA IDENTITY not propagating to partitions; see https://postgr.es/m/201902041630.gpadougzab7v@alvherre.pgsql particularly Robert Haas' comments at http://postgr.es/m/CA+TgmoYjksObOzY8b1U1=bsp_m+702eof42fqrtqtyio1nu...@mail.gmail.com and downstream discussion from there.
