How to remove all sites bar and change the domain name in SharePoint modern site

bhavaM Left side navigation bar on SharePoint sites is called as SharePoint app bar. Unfortunately, you cannot hide SharePoint app bar since March 31, 2023. Check the detailed information at: Introducing a SharePoint app bar that features global navigation 

You maybe be able to hide it using SPFx application customizer and custom CSS/JS injection. Check: How can I include the same JS and CSS files on multiple SharePoint Modern Page?. However such DOM manipulations are not supported by Microsoft and may break in future.

If you are trying to change the links in SharePoint app bar global navigation, check: Enable and Customize Global navigation in the SharePoint app bar 

Note: You cannot change the tenant domain only for specific SharePoint sites. If you change the tenant domain name, it will be changed for all SharePoint sites: Change your SharePoint domain name 

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