All of the examples I found when addressing this had more options specified for the video mode than that (e.g. M or D in the appropriate places). For example video=HDMI-A-1:1024x768@60D is what I have on a headless Pi that I just accessed by VNC to check what was in cmdline.txt (that's on Bookworm though)
/boot/firmware/cmdline.txt adding--> is ignoredCode:
video=HDMI-A-1:1600x900@60
Statistics: Posted by PDM1950 — Tue Feb 10, 2026 10:40 am