Yup, saw this problem for a long time as well on my INTEL NUCs. Tried tons of solutions, but none of them really worked for me.
My work around is a (long) sleep when starting the hyperion service. This was the only way to get it working.
Pls find my service file below.
nano /storage/.config/system.d/hyperion.service
<snip>
[Unit]
Description=Hyperion ambient light systemd service
# After=network.target
Requisite=network.target
Wants=network-online.target
After=network-online.target
After=systemd-resolved.service
[Service]
Environment=DISPLAY=:0.0
User=root
ExecStartPre=/usr/bin/sleep 30
ExecStart=/storage/hyperion/bin/hyperiond --userdata /storage/hyperion/
#TimeoutStopSec=2
#Restart=always
#RestartSec=10
TimeoutStopSec=5
KillMode=mixed
Restart=on-failure
RestartSec=2
[Install]
# WantedBy=default.target
WantedBy=multi-user.target
<snip>