Macbooks flicker on 32" Samsung 4k monitor when too much dark on screen

I have a 32" curved Samsung 4K monitor (model U32R59x, I think) that performs beautifully with both my 2019 Intel MBA and my 2022 M2 MBA...with one incredibly annoying exception. When there is too much dark on the screen, I get an unbearable flicker when there's movement (such as scrolling a 9to5mac browser tab, or "movement" within a YouTube video or game). sometimes it seems like a full-screen flicker; other times it seems like vertical lines flicker (like half of them can render the dark correctly and half cannot).

Sometimes it seems like a sudden transition from dark to light or vice versa triggers it as well.

If I just make the thing that is dark go away, everything is fine.

I have tried two different dongles, plus a USB-C to HDMI cable, plus (as of today) Apple's $69 adapter and their approved belkin HDMI cable. No change. I've tried dozens of color profiles. Some seem....maybe better? but none do away with the problem entirely.

AFAIK, there is no way to update the firmware for this monitor and no updated drivers available that I could find.

Apple chat support eventually referred me to the Genius Bar, who spent ~50m doing diagnostics and then told me he couldn't figure out any reason for it.

Previous (unresolved, archived) discussion threads (like this one) show this happening to multiple people across numerous monitor manufacturers, but not consistently. (my 28" flat 4k Samsung doesn't do it.)

Any ideas? What should I try that I haven't?

PS: this happened in Monterey and happens in Ventura. I think it happened in Big Sur as well.