I had the (low resolution) issue appearing on my second monitor with my M1 Pro on my second external monitor. It's a Samsung 4k display, as is the primary external monitor, although that is plugged into the HDMI port on the laptop directly. I was using a USB-C -> HDMI Female adapter, with a good cable then going into the display. My workaround (and I know everyone won't have this lying around, or have the hardware) was to use a USB-C -> DP (male) cable instead. I know this won't work for everyone, but if it helps some people, so much the better. And yes, the software issue needs to be fixed.