Howto force DHCP server working on a bridge?

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I believe that interface directive only applies to the DNS service and does not apply to the DHCP service (I could be wrong).
The DHCP service listening on port 67 UDP will bind to IP's on all interfaces 0.0.0.0 :

pi@noads:~ $ sudo netstat -nltup | grep 'Proto\|:53 \|:67 \|:80 \|:471[1-8] '
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      15766/pihole-FTL
tcp        0      0 127.0.0.1:4711          0.0.0.0:*               LISTEN      15766/pihole-FTL
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      602/lighttpd
tcp6       0      0 :::53                   :::*                    LISTEN      15766/pihole-FTL
tcp6       0      0 ::1:4711                :::*                    LISTEN      15766/pihole-FTL
tcp6       0      0 :::80                   :::*                    LISTEN      602/lighttpd
udp        0      0 0.0.0.0:53              0.0.0.0:*                           15766/pihole-FTL
udp        0      0 0.0.0.0:67              0.0.0.0:*                           15766/pihole-FTL
udp6       0      0 :::53                   :::*                                15766/pihole-FTL

How is this bridge setup ?

sudo brctrl show

cat /etc/network/interfaces

tail -15 /etc/dhcpcd.conf

ip l

ip a

No Network Manager active ?

sudo service network-manager status

Below some pointers to setup bridge with dhcpcd5 that comes with Pi-hole:

pi@noads:~ $ apt policy dhcpcd5
dhcpcd5:
  Installed: 1:6.11.5-1+rpt7