Avahi alias systemd service. The first file is the script to be run, which you can store in your home directory. The second file is the systemd unit file which goes in /etc/systemd/system. Make sure on line 6 it references the location of the first file, and that you run systemctl daemon-reload after editing the unit file.

avahi-alias.sh

#!/bin/bash
 
local=$(avahi-resolve -4 -n $(hostname).local | cut -f 2)
hostname=$1
 
if [ $local != "127.0.0.1" ]
then
	echo "Aliasing $local as $hostname."
	avahi-publish -a -R $hostname $local
else
	echo "Exiting, local address is $local."
	exit 1
fi

avahi-alias@.service

[Unit]
Description=Publish %I as alias for %H.local via mdns
 
[Service]
Type=simple
ExecStart=/bin/bash -c "/home/osboxes/avahi-alias.sh %I"
Restart=on-failure
RestartSec=5s
 
[Install]
WantedBy=multi-user.target

Thank you very much for your solution!! It works perfectly!!

For others using this on Ubuntu 22+, the bash is located at /usr/bin/bash.