@mm - that probably isn't the issue, but you can adjust /etc/apparmor.d/local/usr.sbin.dhcpd to have:
@{PROC}/sys/net/ipv4/ip_local_port_range r,
and then do: sudo apparmor_parser -r /etc/apparmor.d/usr.sbin.dhcpd # yes, without local/
@mm - that probably isn't the issue, but you can adjust /etc/apparmor. d/local/ usr.sbin. dhcpd to have:
@{PROC} /sys/net/ ipv4/ip_ local_port_ range r,
and then do: sudo apparmor_parser -r /etc/apparmor. d/usr.sbin. dhcpd # yes, without local/