The two latam flights are managed on LATAM with, the QR flights can be accessed by requesting your ticket on LATAMS site in your booking confirm, then you'll be given the partner PNR, which you enter into Qatar's website, where you can add hypothetical FFP to choose seats for free, (OWS and OWG) otherwise its a fee per seat per flight. Hope this helps as both of these airlines, like seemingly every airline has the worst website ever