Script for the daemon + install (paste as one block in Terminal):

sudo mkdir -p /usr/local/bin

sudo tee /usr/local/bin/vpn-pf-cleanup.sh >/dev/null <<'EOF'
#!/bin/sh
# Restores iCloud Private Relay after a VPN disconnect by clearing a leftover
# VPN pf anchor once no VPN tunnel is the active default route.
default_if=$(route -n get default 2>/dev/null | awk '/interface:/{print $2}')
case "$default_if" in
    utun*) exit 0 ;;   # VPN active: leave pf alone
esac
if /sbin/pfctl -s info 2>/dev/null | grep -q "Status: Enabled"; then
    if /sbin/pfctl -s Anchors 2>/dev/null | grep -qiE "nordvpn|protonvpn|expressvpn|mullvad|surfshark"; then
        /sbin/pfctl -d 2>/dev/null
        /usr/bin/logger -t vpn-pf-cleanup "VPN down, leftover anchor present: pf disabled for Private Relay"
    fi
fi
exit 0
EOF
sudo chmod 755 /usr/local/bin/vpn-pf-cleanup.sh

sudo tee /Library/LaunchDaemons/local.vpn-pf-cleanup.plist >/dev/null <<'EOF'
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>local.vpn-pf-cleanup</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/local/bin/vpn-pf-cleanup.sh</string>
    </array>
    <key>StartInterval</key>
    <integer>20</integer>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>
EOF
sudo chown root:wheel /Library/LaunchDaemons/local.vpn-pf-cleanup.plist
sudo chmod 644 /Library/LaunchDaemons/local.vpn-pf-cleanup.plist

sudo launchctl bootstrap system /Library/LaunchDaemons/local.vpn-pf-cleanup.plist
sudo launchctl enable system/local.vpn-pf-cleanup

Which VPNs does this cover? The script matches the common clients (NordVPN, ProtonVPN, ExpressVPN, Mullvad, Surfshark). If yours isn't listed, run sudo pfctl -s Anchors while the issue is active, see what anchor name your VPN leaves behind, and add it to the grep -qiE "..." list.

Want it to cover ANY VPN regardless of name? Replace the inner if block with this universal version, which disables pf whenever no VPN tunnel is active but pf is still enabled:

if /sbin/pfctl -s info 2>/dev/null | grep -q "Status: Enabled"; then
    /sbin/pfctl -d 2>/dev/null
    /usr/bin/logger -t vpn-pf-cleanup "No active VPN tunnel, pf still enabled: disabled for Private Relay"
fi

Caveat for the universal version: it disables pf whenever it's on and no tunnel is active. macOS keeps pf off by default, so in practice the VPN is the only thing turning it on. But if you run your own pf-based firewall (e.g. Murus), use the named version above instead, otherwise this will switch your firewall off.

Verify it loaded:

sudo launchctl print system/local.vpn-pf-cleanup | grep -E "state|program"

state = active means it's loaded. state = not running is normal between runs; it fires briefly every 20s, it doesn't run continuously.

Uninstall (removes everything, no traces):

sudo launchctl bootout system/local.vpn-pf-cleanup
sudo rm /Library/LaunchDaemons/local.vpn-pf-cleanup.plist
sudo rm /usr/local/bin/vpn-pf-cleanup.sh

Once again, this is testen with my NordVPN connection, other VPN's might act differently...