LibreOffice is an open-source office suite software that works across platforms including Windows, Linux, and macOS. Recently, they have improved their User-Interface (UI) and have integrated a Ribbon or Tabbed UI, which has been in use in MS Office since 2007. The new interface is intuitive and simple to use.
To enable the Ribbon or Tabbed UI in LibreOffice 6.2+, the user will have to launch the LibreOffice app in which the interface needs to be changed like Writer (Alternative for MS Word) and go to View -> User Interface -> Tabbed to enable Tabbed user interface as shown below.
Now, the user interface in your LibreOffice app should have changed to the Tabbed Interface.
Repeat this process in any LibreOffice app including Calc and Impress that you want to change the interface in.