LibreOffice has a version for macOS (64-bit).
https://www.libreoffice.org/download/download/?type=mac-x86_64&version=7.2.1&lang=en-US
Make sure the Drop-down Box (1.)
is set for macOS (64-bit) then press the yellow DOWNLOAD
button (2.).
Your help files are online (you have to be connected to the
Internet). This is a difference between the Mac version and the
windows version, there is not yet offline help available yet. When
you download updates, in the future, look for it (Help for offline use: English (US)).
Once the download starts you will get to a page that offers Key
management software. This is if you are into document and
email encryption. Both you and your recipient have to create
keys which will allow only those who have the keys to access
them. Lots of interesting info there even if you don't use it.