How to install wireguard_watchdog on OpenWRT
Run this on your OpenWRT router to automatically re-resolve DNS names for peers.
/usr/bin/wireguard_watchdog
is automatically installed with the standard wireguard package, so you only need to enable it to run every minute:
echo '* * * * * /usr/bin/wireguard_watchdog' >> /etc/crontabs/root
Source: This commit message.