Keep the package luci-app-wireguard installed on OpenWrt. Useful to automatically (re)install the package after a sysupgrade.

install-luci-app-wireguard.sh

#!/bin/sh

[ "${FLOCKER}" != "$0" ] && { exec sh -c "FLOCKER='$0' flock -n '$0' '$0' '$@' || if [ \"\$?\" -eq 1 ]; then echo 'Error: Script is already running.'; fi; exit 1"; } || :

if ! (opkg list-installed | grep -q "^luci-app-wireguard ")
then
        echo "luci-app-wireguard is not installed. Installing and rebooting..."
	logger "$0: luci-app-wireguard is not installed. Installing and rebooting..."
        opkg update && opkg install luci-app-wireguard && echo "Going to reboot in 15 seconds..." && sleep 15 && reboot
else 
        echo "luci-app-wireguard is already installed. Doing nothing."
	logger "$0: luci-app-wireguard is already installed. Doing nothing."
fi

Keep luci-app-wireguard installed on OpenWrt

Usage:

1. Save install-luci-app-wireguard.sh in /root folder (e.g. with vi or with WinScp).

2. Make file executable:
   chmod +x /root/install-luci-app-wireguard.sh

3. Add file to crontab (execute every 5th minute, but then sleep another two minutes before execution):
   echo '*/5 * * * * sleep 120 && /root/install-luci-app-wireguard.sh' >> /etc/crontabs/root

4. Add /root folder to /etc/sysupgrade.conf to keep it when upgrading:
   echo '/root' >> /etc/sysupgrade.conf

5. When upgrading, keep "Keep settings and retain the current configuration" selected.