libnfsidmap was megred into nfs-utils and the bug 504666 was reintroduced. ebuilds (>net-fs/nfs-utils-2.2.1) should pass --with-pluginpath="${EPREFIX}/usr/$(get_libdir)/libnfsidmap" to configure.
$ sudo systemctl status nfs-idmapd.service ● nfs-idmapd.service - NFSv4 ID-name mapping service Loaded: loaded (/lib/systemd/system/nfs-idmapd.service; static; vendor preset: disabled) Active: failed (Result: exit-code) since Wed 2017-12-27 09:23:22 MSK; 4s ago Process: 10599 ExecStart=/usr/sbin/rpc.idmapd (code=exited, status=1/FAILURE) Main PID: 992 (code=killed, signal=TERM) дек 27 09:23:22 home systemd[1]: Starting NFSv4 ID-name mapping service... дек 27 09:23:22 home rpc.idmapd[10600]: libnfsidmap: requested translation method, 'nsswitch', is not available дек 27 09:23:22 home systemd[1]: nfs-idmapd.service: Control process exited, code=exited status=1 дек 27 09:23:22 home systemd[1]: nfs-idmapd.service: Failed with result 'exit-code'. дек 27 09:23:22 home systemd[1]: Failed to start NFSv4 ID-name mapping service.
*** This bug has been marked as a duplicate of bug 642368 ***