So, it turns out the publisher now has my book on "print on demand" status, with the 2018 corrections done, and is not willing to take more corrections – but is willing to publish errata for the two different printings, so I'll work on that. I haven't seen a copy with the corrections yet. I just ordered another off Amazon, where the number of copies available had gone from 10 to 0 after my last message here – thanks to those who bought copies. So I'll see if the "corrected" version is getting through the pipeline yet.
If anyone on the list wants to swap an old copy for a corrected copy, signed, I'm still willing, assuming I can get them.
Publishing errata online will let me go into a lot more depth on some of my confusions in the book, like about the impulse invariance method of discrete-time filter design, which has some subtleties that I was confused about.
The Japanese translation has most of the errors corrected, since most of the post-2018 errata came from the translator.
Our internal course at Google has completed Part IV, and is starting Part V next week, finishing up by March, at a chapter every other week. With luck, I can eventually get videos released. It has been a lot of fun, working with "students" around the globe that I've never met in person. A good use of pandemic time.
Dick