Systemd timer as user - not starting at boot

Example of service/timer construct.
source → [root tip] [HowTo] Check if your AUR build scripts have been updated

 $ cat check-aur.service
[Unit]
Description=Check for changes to AUR buildscrpts
# wait for network
After=syslog.target network.target default.target

[Service]
Type=simple
ExecStartPre=/bin/sleep 30
ExecStart=/home/%u/.local/bin/check-aur.sh

[Install]
WantedBy=default.target
 $ cat check-aur.timer
[Unit]
Description=Schedule AUR change checks

[Timer]
OnStartupSec=10m
OnUnitActiveSec=4h

[Install]
WantedBy=timers.target