Stream from a Linux Sunshine host to devices with non-standard native panels — a 19.5:9 phone (2416×1080@120), a notched MacBook Air 15" M2 (2880×1864@60), a 16:10 120 Hz tablet (2560×1600@120) — at each device's exact resolution and refresh, so nothing is letterboxed or downscaled.
The trick: add custom modes to the EDID of the headless HDMI dongle the host renders to, then point per-client Sunshine apps at those modes.