version 2 is a bit faster and cleaner because it uses omada's list of clients instead of scanning the whole subnet:

#!/usr/bin/bash

version=0
changelog="version=$version, 13-Jun-2024, initial build"

version=2
changelog="version=$version, 14-Jun-2024, swapped loop from by-subnet to by-omada-clients-mac, saving before and after files in /var/tmp"


HELP="
dns2omada.sh is the most simplistic script ever meant to paliate one of dumbest laziest lack of feature of the tp-link OMADA SDN software....
it simply populate the OMADA client's name based on DNS name...  everytime the script runs it will keep a copy of the omada clients output
before and after the script execution in /var/tmp/omadaclients.*.dns2omada

using a python omada api...
Assumptions:
- you already have a local DNS server able to perform reverse DNS resolution per IP.
- you already have omada SDN setup on the network
- you should create an OMADA admin account dedicated to this process using a very long random password string without any special character
- my subnet is simply from 192.168.0.1 to 192.168.0.256 so I have a simple loop, you might have to modify the script if your subnet is class B
with an outer loop etc...
usage:
    1) install python: sudo apt install python3-pip
    2) install the omada python api: pip install tplink-omada-client
    3) update the parameters CHANGE_ME values in the scipt below
    4) run the script manually or in cron...    
"


# these should be self-explanatory
omada_username="CHANGEME_mrpotatoe"
omada_password="CHANGEME_lfdaruiRWGFD335qw324z"
omada_site="CHANGEME_homesweethome"
omada_url="https://CHANGEME_omada.mylocaldomain"
dns_server=CHANGEME_192.168.0.1
omadabin=/CHANGEME/bin/omada   # the absolute path to the omada binarie whch gets installed with the client.




if [[ $# -gt 0 ]]
then
    echo $HELP
    exit 3
fi

if fgrep -v grep $0 | fgrep CHANGEME  >/dev/null
then
    echo "ERROR: you forgot to change these varialbes from $0:"
    fgrep -v grep $0 | fgrep CHANGEME
    echo "$HELP"
    exit 4
fi

$omadabin -t myomada target --url $omada_url --user $omada_username --password $omada_password --site $omada_site --set-default
omadaclients=/tmp/omadaclients.$$.txt
$omadabin clients  > $omadaclients


cat $omadaclients | while read mac ip name device port junk
do
    clientname=""
    clientmac=$mac
    #
    # debugging
    # echo "parsing mac=$mac ip=$ip name=$name device=$device port=$port junk=$junk"

    if [[ $ip = "" ]] || [[ $ip = "-" ]]
    then
        echo "skiping $mac because omada does not have an IP for it"
    else    
        clientname=$(nslookup $ip $dns_server 2>/dev/null | fgrep "=" |cut -f2 -d"=" |cut -f1 -d"."|tail -1)
        if [[ $clientname = ""  ]]
        then
            echo "skipping $ip because I cant resolve it"
        else
            echo "setting hostname for $ip to $clientname for mac $clientmac "        
            $omadabin set-client-name $clientmac $clientname            
        fi
    fi
    unset  mac ip name device port junk    
done
cat $omadaclients > /var/tmp/omadaclients.before.dns2omada
$omadabin clients  > /var/tmp/omadaclients.after.dns2omada