cosmic-greeter freezes when system is powered on with more than one monitor

[d-val-r]

I have two Westinghouse WH23FX9019 monitors, both connected via HDMI to my AMD Sapphire NITRO+ RX 580. I am using the 24.04 alpha ISO, freshly installed.

When launching my machine from cold boot, I get past the encryption password, and it goes to cosmic-greeter on one monitor. The other remains a dark gray-blue color. The screen with cosmic-greeter stay frozen. I can't enter my password or click buttons, even though I can move the mouse.

Disconnecting the other monitor does not resolve the issue unless I reboot and have the system come up with only one monitor from a cold boot. Then cosmic-greeter works fine. Reattaching the second monitor after logging in results in it coming up without issues. I can even suspend the machine, go back to cosmic-greeter with both monitors, and it works fine, so long as I do not reboot with both monitors attached at once.

I have tried changing out the offending monitor's HDMI cable for an HDMI to VGA cable. The result is that that monitor came up, not the usual one, so I don't think it's the cable. It doesn't matter which monitor is plugged in - either one works if it's the only one plugged in, and one will fail if they are both plugged in when booting.