Use domain2 to point to domain 1 without using DOMAIN ALIASES

I’m hosting software on but would also like to have to point as well without adding it to examplecom DOMAIN ALIASES. I am hosting a SAAS and user are allowed to add own domain. I want them to be able to add eample3 or domain1. com or domain 3…ext. and have it work without me having to add those domains manually to domain aliases. ( software im using allows user to add custom domain)
in the software setup i got the following code. How would i modify Vhost with or change Vhost to make things work.

<VirtualHost *:80>
ServerAdmin webmaster@localhost
DocumentRoot /var/www/html/public/

    <Directory /var/www/html/public>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    <IfModule mod_dir.c>
        DirectoryIndex index.php index.cgi index.html index.xhtml index.htm

Thank You all