New install folder confirmation

Platform is a raid1 configured Dell OptiPlex 7050 with Devuan Linux and nginx and ufw.
The goal is to serve a blog, web pages, and maybe some other things.
I did the preparation in Step 4 here https://www.techlear.com/blog/2019/07/05/how-to-install-grav-cms-with-nginx-on-debian-9/
Then I followed grav install instructions here https://learn.getgrav.org/16/basics/installation ...
I downloaded the .zip and moved it to /var/www/grav then unzipped it.
It created a new directory/folder /var/www/grav/grav-admin
Then I ran

sudo chown -R www-data:www-data /var/www/grav

Question: Is that all correct?

When you go to your website for the first time do you get the create admin login page?
If so its probably alright as the initial page does check that most features are installed.

When you refer to "your website" I think that because this is a server install - that I may have missed a step.

I presume that the default ~/user/pages/01.home/default.md page isn't expected to display at "localhost" but, rather, at the URL I provided when I set up Devuan in Server mode and (I think) that I may have provided to nginx when installing it?

Or, am I getting ahead of myself and over-thinking this at this step?

EDIT1: I read, somewhere, that grav cannot be run without a theme and there's no default theme - so, In Linux:
ln -s user/themes/quark /var/www/grav-src/user/themes/quark solves that. Is this old and a default theme is now installed?

EDIT 2: I read in the grav configuration documentation that I may need to add a custom_base_url: ' ' to ~/user/config/system.yaml

EDIT 3: Was this a correct or incorrect thing to do? "Change ownership of the /var/www/grav directory to www-data:

sudo chown -R www-data:www-data /var/www/grav
```"

EDIT 4: Step 3 here [https://www.techlear.com/blog/2019/07/05/how-to-install-grav-cms-with-nginx-on-debian-9/](https://www.techlear.com/blog/2019/07/05/how-to-install-grav-cms-with-nginx-on-debian-9/) says Run sudo vim /etc/nginx/sites-available/grav.conf and populate the file with the following configuration:

server pl

Activate the new grav.conf configuration by linking the file to the sites-enabled directory.

sudo ln -s /etc/nginx/sites-available/grav.conf /etc/nginx/sites-enabled

Check NGINX configuration for syntax errors:

sudo nginx -t

The "sudo nginx -t" test generates a "test failed" error.