After installing tailscale, follow arch wiki to unmanage tailscale0 interface from NetworkManager (if you’re using it).
Now, if your MagicDNS do not work after a system sleep:
reason: etc/resolv.conf gets overwritten by NetworkManager. To fix this follow tailscale docs, and configure NetworkManager to use systemd-resolved for DNS configurations (arch wiki)
sudo ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
sudo cat << EOF > /etc/NetworkManager/conf.d/dns.conf
[main]
dns=systemd-resolved
EOF
sudo systemctl restart systemd-resolved
sudo systemctl restart NetworkManager
sudo systemctl restart tailscaled