What is the latest stable version of LO 6 for old Ubuntu 16.04 LTS.
Thanks!
I guess, the one that you can find in the Ubuntu repos.
The download page currently offers 6.3.5 .deb (choose your operating system). Note that it is a LibreOffice_6.3.5_Linux_x86-64_deb.tar.gz file that you need to unpack into a temporary directory which creates several .deb files you have to install from there. See https://wiki.documentfoundation.org/Installing_in_parallel/Linux#Step_2:_Downloading_and_Unpacking_the_Installation_Files