I could select seats for the JL flights in the JL app. QR flights I can choose in the QR app. BA Silver status probably helps.
Got a schedule change on the connecting JL flight on the outbound by 25 mins (does not change the flights significantly, only shortens the transfer time in DOH) and I could change the flights/dates for free on the JL app/website. Got offered BA to LHR from BER in J and then LHR-HND in J again on the A350-1000. Pretty happy to get the A351 for 600 EUR per way 🤣