I have two identical external monitors. When both are active, they show a message “the current input timing is not supported. Please change your input timing to 1920×1080, 60hz, or any other monitor listed timing as per the monitor specifications.” If I deactivate either monitor in arandr, the other works. I’ve tried both monitors connected via USB C, one with USB C and one with HDMI, and one with HDMI and one with an external powered adapter (USB C to the computer, HDMI to the monitor).
I’ve gone into arandr and activated one, then the other, to confirm that either works. I’ve also gone into nvidia-settings and explicitly set both to 1920×1080 and 60hz.
I’ve tried both with i3 and Gnome.
I am using nvidia-driver-460.
The computer is a Lenovo Thinkpad P1 Gen 2. Neofetch says I have two graphics cards: “NVIDIA Quadro T2000 Mobile / Max-Q” and “Intel UHD Graphics 630”.