Dear @_tmp, thanks for taking the time to reply.
I’ve read the unbricking thread and tried to enter EDL, but it does not come up. I’ve tried multiple times to do what you suggested, with the volume buttons. It always registers as 05c6:900e instead 
I am obviously hesitant to perform the disassembly to the mainboard and short the debugging contacts as described by calvofl0, because I assume that would void my warranty. Do you know whether it does? Does the support recommend this procedure?
On a side note: I don’t remember whether I’ve enabled encryption. If I did, is there any way to decrypt the flash image, in case I a) get access to it, e.g. through EDL, and b) still know my PIN?