Update: From what I've seen so far, it seems that the easiest way to get a good boot image is to find the OTA file after it is downloaded but before it is installed. I'll provide another update if I can find a way to get the boot image extracted properly, but for now, unless someone else has the 20200306 image, we might have to wait a few more days for the next update.
(Alternatively, is it possible to safely downgrade the device and use an older boot image to root? There were some messages that implied it might be possible, but I want conformation from someone who knows what they are doi