Despite the bad news, I’ve built and flashed again, just because I’m still curious. 
But I still have the same problems as before. Though, I did notice that rushing through the setup by clicking “Next” all the time is possible. That way, I was able to get to the start screen before the crash happened. After the crash, I had to reboot. But as the setup had been finished this time, the phone booted directly to the start screen. So, at least, the OS is working for some seconds. Anyway, another remark: I have the feeling that it always takes the exact same amount of time for the crash to happen.
Is it possible to get some logs about the crash? I thought adb logcat is the approach for this, but as far as I understand it, adb needs to recognize the device as “online”/“active” for this. However, with the phone plugged in and in recovery mode, I get this:
$ adb devices
List of devices attached
ed44b624 offline
and then I get nothing with adb logcat after a reboot. Any hints how to obtain a log? Otherwise, I’ve no idea what else to do and I’m also a bit tired of building and flashing anymore (unless there is new progress indicating a possibly successful new attempt).