How to install LibreOffice for all users on Windows 10?

Subject seems to cover the question pretty well. Only extension I can think of is to note that it’s already installed now, so I’d prefer to modify it without a complete reinstallation. And yes, I did search for the answer during the initial installation.

(The menu language switch was possible without reinstalling, but it was definitely tedious.)

LibreOffice is installed for all users on Windows using its MSI packages; it doesn’t have a “install for current user only” mode. So your question is unclear: what specifically did you try, and what specifically does not work?