Default pepper.conf does not set DNS1 IP address (line 70 #dns1 192.168.182.254).
But the default IP received by DCHP is 192.168.182.1 (cf. /etc/resolv.conf on client).
When pepper tests a packet (see dhcp.c dhcp_doDNAT() lines 2045-2050) it fails !
So we must set DNS1 directive, with the corect default value) in pepper.conf (or activate uamanydns).
PS : Local DNS service must be started AFTER pepper in order to enable DNS to listen to tun0 ip address (ie. 192.168.182.1 by default)