Ubuntu should provide an easy way to share, out of the box.
At the moment, in 18.04 in GNOME Settings > Sharing, the only thing that can be done out of the box is to change the computer name.
So, out of the box, in Sharing there is no option to share something.
File Sharing - WebDAV
The default File Sharing is done via WebDAV and is shares a user’s the Public directory.
It requires apache2 and libapache2-mod-dnssd but they are not installed by default.
I suggest to include apache2 and libapache2-mod-dnssd in the installation media in order for WebDAV to work.
Media Sharing - DLNA
The DLNA server is rygel (rygel-preferences is not needed). If it is installed, it shows up in Settings > Sharing as Media Sharing.
The DLNA client for videos is GNOME Videos (or your TV) but it requires grilo-plugins-0.3-extra to be installed and by default it’s not.
After installing it, if there is a DLNA server on the network, it will appear in GNOME Videos in the Channels tab.
Rhythmbox can play music from DLNA if grilo-plugins are installed and if the Grilo media browser Rhythmbox plugin is enabled. The DLNA server shows in the left sidebar (maybe you need to click on the + sign and click on Check for new devices).
I suggest to include rygel and grilo-plugins in the installation media in order for Media Sharing to work. I also suggest enabling the Rhythmbox Grilo media browser by default.
With WebDAV a user can easily share the files from the Public directory and with DLNA they could also share their Videos directory (or any other media directory).
Windows file sharing - Samba
There is an ongoing discussion about it, but if Samba is installed, it should show up in Settings > Sharing.
At the moment, it does not.
I think Samba should be removed from Nautilus from the directory properties (Local network share) and also from the right click menu (Local network share).
It is not the default way of sharing files (WebDAV is) so it does not belong in Nautilus.