This struck a chord: "I really hope he's still around to see them in print. Quite frustrating, to be sure." Lee is 87; I am 72 and in good health but as you probably saw even if were accepted, Steidl requires that the artist make 3 trips (of course his hands on approach at every point along the way is appreciated) before everything is finalized & approved. If he does only one book at a time, and I have no reason to doubt him, & being that he is already behind his original schedule for publishing two books, is a bit alarming; 3 people who were influential in my life passed away before 70 quite suddenly meaning they had not been sick; this makes me acutely aware of my own mortality (not in a once in a while morbid way) which is said to be an important thing. Not quite the same thing but it reminds me of authors who sell the rights to their book to a film studio, and the book never makes it to see the light of day; even allowing the intentions were pure the net result is the work is tied up, never to be produced sitting on an office shelf somewhere.
Be prepared to invest a lot of time and money in this project. You will need to scan or digitally photograph all your prints and adjust them to you liking. Or scan the negatives and redo all the work you did in the darkroom. That involves either outsourcing or an investment in decent equipment and software, plus the skills to use them. Even if the publisher or printer you end up with will rescan the photos, you will need something to put together a proposal and mock-up of the book to shop around. And if you self-publish, it is all on you or whoever you hire. Also, if you self-publish, you will need to sell and distribute the books somehow. Many bookstores won't take self-published books, leaving online sales and maybe a gallery or other outlet.
Steidl is good, but not the only game in town. If you haven't already read it, Jonathan Blaustein's post on book publishing (
https://aphotoeditor.com/2022/01/28/this-week-in-photography-making-a-book/) is a pretty good, if wordy, assessment of the process today. Your best and quickest way to get published is to self-publish. Do some serious research, there are a lot of sources. I have used Bookmobile in Minneapolis as a moderately-priced, quality printer. But I don't think they do some of the more sophisticated techniques like duo- or tritone black printing. And if you don't have the design or editing chops, hire someone who does or you will most likely be disappointed. Even publishers like Steidl will charge you a good sum to cover some or all of the prepress work involved, unless you are a known quantity that will guarantee sales.
In the end, maybe a limited edition portfolio is the best way to go if you have a gallery or know enough collectors to make it worthwhile. Diane Arbus made a portfolio of 10 prints (in a custom acrylic case that could be used as a frame for display) while she was alive. She made 8 of a projected edition of 50 and she only sold 4 of them.