Comment 14 for bug 1726124

This change in behavior is deliberate. There are two mutually incompatible interpretations of DNS search lists provided via a VPN connection. One is for split DNS, to say "this is the list of domains for which you should send lookups to the accompanying DNS server". The other is to use it as a search list for resolv.conf. Unfortunately, interpreting wrongly in either direction breaks client configs. But whereas there are other ways that one can configure the behavior of resolv.conf to add search domains, the only reasonable way to configure split DNS is to do so by providing this information directly from network-manager-openvpn to systemd-resolved.

It may be that network-manager-openvpn needs an additional configuration option, to allow the user to declare which of these two ways (or both, or neither) they want to use the VPN server-provided DNS search list.