Port forwarding as described did not work for me.
Also the solutions with setcap don’t work (Java won’t work anymore).
But the solution with socat works! To make it autostart, I put the following in /etc/rc.local:
# DHCP-Listening Openhab
(socat UDP4-LISTEN:67,fork UDP4-DATAGRAM:192.168.0.255:6767,broadcast) &
(socat UDP4-LISTEN:68,fork UDP4-DATAGRAM:192.168.0.255:6767,broadcast) &
(socat UDP4-LISTEN:67,fork UDP6-DATAGRAM:192.168.0.255:6767,broadcast) &
(socat UDP4-LISTEN:68,fork UDP6-DATAGRAM:192.168.0.255:6767,broadcast) &
About the last 2 lines I’m not sure if they are necessary.
The property uses_dhcp_listen still shows no, but this is wrong, it’s working immediatly.