Should I use FQDN or hostname only in OpenWrt

Installing and Using OpenWrt Network and Wireless Configuration
11

I'm hitting related issues right now running 22.03.5 and I can with impunity say that it sets the hostname only.
You can verify this with cat /proc/sys/kernel/hostname and cat /proc/sys/kernel/domainname

AFAIK, the correct way to set the domainname is to make a file in /etc/sysctl.d/
This is a fairly fundamental setting so I called it 01-domainname.conf (they are executed in the listed, alphanumeric, order.)

Contents of the file should be:
kernel.domainname=<yourdomainname>

No quotes around the yourdomainname.

Then run /etc/sysctl restart and cat /proc/sys/kernel/domainname again to verify.
Now the domain is set in the kernel.

I didn't see a way to install inetutils to get the hostname utility so here's a script that mimic's it. (Put in /usr/bin and chmod +x /usr/bin/hostname so it can execute.)

#!/bin/sh

fqdn=0
domainonly=0
while getopts 'dfs' c; do
    case $c in
    d) domainonly=1 ;;
    s) fqdn=0 ;;
    f) fqdn=1 ;;
    *)
        printf "%s [-dfs] \n" "$0"
        printf "Options:\n"
        printf "\t-d: DNS domain name\n"
        printf "\t-s: \"short\", hostname only\n"
        printf "\t-f: FQDN\n"
        exit
        ;;
    esac
done

if [ "$domainonly" != "0" ]; then
    cat /proc/sys/kernel/domainname
elif [ "$fqdn" != "0" ]; then
    printf "%s.%s\n" "$(cat /proc/sys/kernel/hostname)" "$(cat /proc/sys/kernel/domainname)"
else
    cat /proc/sys/kernel/hostname
fi