mpvremote fails to start when starting mpv as a systemd service

I was trying to setup a systemd service to autostart mpv on boot. However mpvremote fails as follows:

systemctl status mpv-start
● mpv-start.service - Start mpv
     Loaded: loaded (/etc/systemd/system/mpv-start.service; enabled; preset: disabled)
     Active: active (running) since Wed 2023-08-23 23:06:27 CEST; 7s ago
   Main PID: 28301 (mpv)
      Tasks: 9 (limit: 9365)
     Memory: 23.7M
        CPU: 155ms
     CGroup: /system.slice/mpv-start.service
             └─28301 /usr/bin/mpv --vo=gpu --gpu-context=drm --drm-connector=HDMI-A-1 --idle

Aug 23 23:06:27 n411z systemd[1]: mpv-start.service: Scheduled restart job, restart counter is at 1.
Aug 23 23:06:27 n411z systemd[1]: Started Start mpv.
Aug 23 23:06:27 n411z mpv[28301]: [mpvremote] true
Aug 23 23:06:27 n411z mpv[28301]: [mpvremote] {"error_string":"init","killed_by_us":false,"status":-3,"stderr":""}
Aug 23 23:06:27 n411z mpv[28301]: [mpvremote] ""

The same command starts mpv and mpvremote successfully when executed on the terminal.

husudosu / mpv-remote-node

mpvremote fails to start when starting mpv as a systemd service #20