[stumped]

ok. so once I sorted my serial number and plug ins out. I could de-drm a azw file that amazon sends for a transfer via USB, for a book published jan 3.

that's a sample of 1, so no guarantee I could do that for ANY book, but maybe the current advice for OP is that if you buy a cheap old e-ink kindle from somewhere, then there';s a simple working method to get newly published books into calibre. no need to use kindle for PC at all.
Amazon could close that loophole at any time though

I don't have any new book purchases planned, so I can't do more testing, outside of prime reading, for now.

and maybe expensive new books have more elaborate protection