I have installed Linux Mint 18.04, and Ubuntu 18.04 + Cinnamon. On Linux Mint, Nemo shows a much better context menu and the file property dialogue box has "Share". On Ubuntu + Cinnamon, Nemo shows simpler a context menu, and the "Share" tab is missing.
I have searched the web, and the answer was installing "nemo-share", but there was no such thing on Ubuntu. I have seen this page, and added
ppa:webupd8team/nemo. Why can't I find nemo-share? The versions of both Nemo were exactly the same: 3.6.5.
PS: It seems that the update failed.
sudo apt update ... Ign:7 http://ppa.launchpad.net/webupd8team/nemo/ubuntu bionic InRelease Err:8 http://ppa.launchpad.net/webupd8team/nemo/ubuntu bionic Release 404 Not Found [IP: 188.8.131.52 80] Reading package lists... Done E: The repository 'http://ppa.launchpad.net/webupd8team/nemo/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.
When I searched Google for "nemo ubuntu", there were two repositories, one from WebUpd8 and one from NoobsLab. Both had the same error message when updating.