The page shown at that domain looks like a default page provided by some other web server software (Apache, I think) which might mean you’ve created your VPS using a LAMP image.
When you created the VPS, did you choose an option that mentioned anything about hosting websites? If so, it may be worth recreating the VPS with a different image, a base Ubuntu image which doesn’t include any software for web hosting.
If you follow the recommended installation process you can’t have another web server installed so you would need not to have apache. There are topics about installing discourse with other web servers.