How to hide or remove quick launch left navigation from SharePoint Online Modern site page

❓️ Why hide SharePoint quick launch ?

Modern SharePoint templates like Communication Sites use navigation menu and give more wider page width allowing you to display more content on the page. It does not provide the left navigation links.
You can even hide the quick launch on Teams Sites by unselecting it from the Navigation settings.

⛏️ How to hide quick launch in Modern SharePoint site ?

1. Navigate to SharePoint Modern site.
2. Click Settings.
3. Click Site Information.
4. Click View all site settings.
5. Under Look and Feel, click Navigation Elements.
6. Click OK.
7. Uncheck Enable Quick Launch.

⛏️ How to hide quick launch in Classic SharePoint site ?

Add Content/Script Editor web part on the page and add script to hide the HTML DIV element.
Add display:none.

<style type="text/css">  
 #spLeftNav {display: none}  
</style>

spLeftNav = respective navigation main div element.