Thnx @stephdl for the quick response. Good to know we have a reaonably safe option to install nextcloud 12.
The reason I am pushing this is that IMO we can not afford to stay on an old version of nextcloud (currently NC 10 is default for NethServer) and see that options and possibilities are passing us left and right.
If we want to be able to be a viable alternative to, for example G-Suite and Office365, dropbox etc, we need the latest version of (in this case) Nextcloud available, preferably with LibrOffice Online/Collabora Online integration. Or as @ghost mentioned in So, what are you working on? - 22 May 17 : OnlyOffice
Especially if we want to push NethServer forward in office and educational environments I think this is important.