Thanks again all who commented, and apologies to Terry for sidetracking the thread (though it is still about the OP camera).
As I said, I've been thinking about that Sony RX10 IV. Something that bothered me is the 1" sensor (noise) and not-so-shallow depth-of-field. Also, the idea that I would be carrying at least three or four less-often used focal lengths (300mm to 600mm) all the time. I am sure those super telephotos would open new possibilities, but still... not something used most of the time. And the price, of course, even if in the States it is "only" about $1600.
I am currently leaning toward a somewhat surprising choice: a quirky little Canon M6 Mark II. On the plus side: 32.5 Mpx APS-C sensor, native miniaturized lenses (especially the high-speed pancake 22/2 - eqv. 35mm). I am also going to get a kit lens, 18-150 (eqv. 28-240) that should be my standard walk-around lens. As I like a shallow-depth of field, in particular for portraits, Sigma is about to ship its 56/1.4 (eqv. 90mm). All three lenses, body, plus that quirky viewfinder, would be about $2,000. Weight? 1093 grams (2.4 lbs).