Even with nss_resolve, you still have to have /etc/resolv.conf correctly populated, because some apps will ignore gethostbyname() and just parse resolv.conf and

Even with nss_resolve, you still have to have /etc/resolv.conf correctly populated, because some apps will ignore gethostbyname() and just parse resolv.conf and do DNS by themselves. For example, golang stdlib does that (but to the credit of golang runtime, it checks whether nsswitch.conf is in expected state and falls back to glibc if it is not). Some apps go even further and do their DNS entirely on their own (Firefox DoH controversy). nsswitch however doesn't just configure mechanism for public resolver, it is a hook where alternate mechanisms like nss-mdns or nss-mymachines can hook up.