The issue was that my previous .DEV website had to use HTTPS, which meant installing SSL certificates on my EC2 server.

To get that information, I contacted Namecheap customer support, where they informed me of the above requirement. Thanks Namecheap, response was quick (within a couple of hours).

So I followed the last few minutes of this tutorial: https://www.youtube.com/watch?v=8Uofkq718n8

Installed SSL certificates with Certbot; got more help from ChatGPT and used :

sudo apache2ctl configtest

To troubleshoot root directory issues and voila, finally got my website to work with a Namecheap domain name.