Acessing my domains URL without "www"

Technically speaking it’s your webhost.

I would redirect via .htaccess

# Force the "www."
RewriteCond %{HTTP_HOST} !^www\.domain\.com$ [NC]
RewriteRule ^(.*)$ https://www.domain.com/$1 [R=301,L]

I didn’t changed .htaccess and now everything looks be fine with the primary domain. However, I can access my subdomain with the www but when I try without the www it redirects me to the primary domain.

It’s strange because I have another multisite blog in the same host and it’s all ok.

Thanks!

In my subdomain page, every link takes me to the primary domain homepage.

Ah, okay, subdomains. Use this:

# Force the "www."
RewriteCond %{HTTP_HOST} ^domain\.com$ [NC]
RewriteRule ^(.*)$ https://www.domain.com/$1 [R=301,L]

When I try access editorial.stationeryoverdose.com still redirecting me to my primary domain.

If I type the www, I can access my subdomain but links still redirecting me to my primary domain.

When I try access wp-admin without the www, I am redirected to the homepage. Isn’t a big problem for me, but that’s normal?

it’s normal, but it’s your server, and you may want to ask your webhost how to do it properly.