The main branch does not resolve DNS properly, resulting in a network but no Internet access!

Compiling master branch firmware in the routing use of the network but can not access to the Internet, it is found that DNS is not normal resolution caused. The dnsmasq and odhcpd packages that replaced 19.07 still have this problem after compilation, and it is not known where the problem is caused. After check/var/etc/dnsmasq. Conf without this file, check the/etc/resolv. Conf file, found that record the value of "search LAN nameserver" rather than "search LAN nameserver", check the TMP/resolv. Conf., d/resolv. Conf. Auto file, found that only "# Interface wan" records。 How to deal with it?

What is the output of:
uci export network; uci export dhcp; ls -l /etc/resolv.* /tmp/resolv.*; head -n -0 /etc/resolv.* /tmp/resolv.*