Nice. I think I might keep an eye on potential rumors of a Libra 3 or something like that given that the Libra 2 came out in 2021, that's nearly 3 years old.
But that gives me time to save a few buckets as well. For now the Oasis is working well enough, just it'd be nice to get away from some of the paper cuts.
Same here with me and the color versions here. If and when I need to replace what I have now, or maybe a software update makes me want to throw them out a window or something, then I'll take a look at the new options. It's highly unlikely I'd get rid of my currently working and mint condition and known-good readers before that.
Calibre works well for the Libra 2. I have a plugin that automatically reformats epubs as kepubs (see https://wiki.mobileread.com/wiki/Kepub). That's not a hard requirement but it improves the reading experience a little bit. The biggest difference I notice is that it makes page numbers handle font size changes more accurately. If I halve the number of words that'll fit on the screen, the reader shows that the number of pages in the book has doubled. Also, the current page number increments every time I turn a page, not just when I cross an invisible page boundary.
It's not a dealbreaker not to have those things, but they're nice and worth the 30 seconds to enable in Calibre.