By default, you won’t find “Sign as different user” option in SharePoint, but most of them as a developer or superuser need to log in with different users to see the content rendering based on different permission and role. So there are two ways to open the SharePoint site in different users.
You need to just append “_layouts/closeConnection.aspx?loginasanotheruser=true” to your Site Absolute Url and just hit enter, it will show you the pop up for credentials. There is no browser restriction for the same.
This method is only applicable in the SharePoint on-prem site.
The second method is to run a user browser to “Run as different user” mode. So to open any browser as the different user just simply press shift and right-click on the browser exe file, it will show you the option “Run as different user”, select this option and it will pop up for credentials. Enter the credentials for the user which you trying to log in and open your SharePoint site.