Just tried this
apt-get -y remove isc-dhcp-server
apt-get -y remove libdns-export1109/focal-proposed
apt-get -y remove libirs-export161/focal-proposed
apt-get -y remove libisc-export1105/focal-proposed
apt-get -y install isc-dhcp-server
apt-get -y install libdns1109/focal-proposed
apt-get -y install libirs161/focal-proposed
apt-get -y install  libisc1105/focal-proposed


GW1
#  dpkg -l | grep isc-dhcp-server
ii  isc-dhcp-server                      4.4.1-2.1ubuntu5                   amd64        ISC DHCP server for automatic IP address assignment
#  dpkg -l | grep libdns
ii  libdns-export1100                    1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported DNS Shared Library
ii  libdns-export1109                    1:9.11.16+dfsg-3~build1            amd64        Exported DNS Shared Library
ii  libdns1109:amd64                     1:9.11.16+dfsg-3~ubuntu1           amd64        DNS Shared Library used by BIND
# dpkg -l | grep libirs
ii  libirs-export160                     1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported IRS Shared Library
ii  libirs-export161                     1:9.11.16+dfsg-3~build1            amd64        Exported IRS Shared Library
ii  libirs161:amd64                      1:9.11.16+dfsg-3~ubuntu1           amd64        DNS Shared Library used by BIND
# dpkg -l | grep libisc
ii  libisc-export1105:amd64              1:9.11.16+dfsg-3~build1            amd64        Exported ISC Shared Library
ii  libisc-export169:amd64               1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported ISC Shared Library
ii  libisc1105:amd64                     1:9.11.16+dfsg-3~ubuntu1           amd64        ISC Shared Library used by BIND
ii  libisccc161:amd64                    1:9.11.16+dfsg-3~ubuntu1           amd64        Command Channel Library used by BIND
ii  libisccfg-export160                  1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported ISC CFG Shared Library
ii  libisccfg-export163                  1:9.11.16+dfsg-3~build1            amd64        Exported ISC CFG Shared Library
ii  libisccfg163:amd64                   1:9.11.16+dfsg-3~ubuntu1           amd64        Config File Handling Library used by BIND



GW2
# dpkg -l | grep isc-dhcp-server
ii  isc-dhcp-server                      4.4.1-2.1ubuntu5                   amd64        ISC DHCP server for automatic IP address assignment
# dpkg -l | grep libdns
ii  libdns-export1100                    1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported DNS Shared Library
ii  libdns-export1109                    1:9.11.16+dfsg-3~build1            amd64        Exported DNS Shared Library
ii  libdns1109:amd64                     1:9.11.16+dfsg-3~ubuntu1           amd64        DNS Shared Library used by BIND
# dpkg -l | grep libirs
ii  libirs-export160                     1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported IRS Shared Library
ii  libirs-export161                     1:9.11.16+dfsg-3~build1            amd64        Exported IRS Shared Library
ii  libirs161:amd64                      1:9.11.16+dfsg-3~ubuntu1           amd64        DNS Shared Library used by BIND
# dpkg -l | grep libisc
ii  libisc-export1105:amd64              1:9.11.16+dfsg-3~build1            amd64        Exported ISC Shared Library
ii  libisc-export169:amd64               1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported ISC Shared Library
ii  libisc1105:amd64                     1:9.11.16+dfsg-3~ubuntu1           amd64        ISC Shared Library used by BIND
ii  libisccc161:amd64                    1:9.11.16+dfsg-3~ubuntu1           amd64        Command Channel Library used by BIND
ii  libisccfg-export160                  1:9.11.3+dfsg-1ubuntu1.12          amd64        Exported ISC CFG Shared Library
ii  libisccfg-export163                  1:9.11.16+dfsg-3~build1            amd64        Exported ISC CFG Shared Library
ii  libisccfg163:amd64                   1:9.11.16+dfsg-3~ubuntu1           amd64        Config File Handling Library used by BIND



still not good