Kinda hard to encode it in /etc/passwd, which separates entries with newlines and fields of an entry with colons.

Of course, you can activate some alternative user database in /etc/nsswitch.conf and then you can have your usernames with newlines in them, but at least half of the tools on your system that process usernames will take that personally…

ps outputs a newline after every entry. What are you trying to accomplish?

Do you have a username that contains a newline character? If so… why?!

Yes; I wanted to mention that dhcpcd is not affected because the title explicitly mentions the DHCP client (dhclient), so people might go looking for alternative DHCP clients in the comments.

I think it’s a bit confusing that you mentioned the DHCP client (dhclient) and DHCP relay (dhrelay) in the title, then link to the Arch Wiki article about the DHCP server (dhcpd). Yes, dhrelay is contained in the dhcpd package (dhclient, however, is not), but I assume most people will be using a DHCP client and few will be operating a DHCP server or relay.

On Arch, the client is in the dhclient package, which is generally also the name of the ISC DHCP client binary.

dhcpcd (DHCP Client Daemon) is not affiliated with the ISC and still appears to be under active development.