$ mount /mnt/ Unprivileged user can not mount NTFS block devices using the external FUSE library. Either mount the volume as root, or rebuild NTFS-3G with integrated FUSE support and make it setuid root. Please see more information at http://tuxera.com/community/ntfs-3g-faq/#unprivileged
and of course
systemctl --user start mnt.mount Failed to start win10.mount: Unit win10.mount failed to load: No such file or directory.
and without "--user" it requires root-access. however, I haven't set up any kind of sudo, but yet whenever I plug in an ntfs drive KDE Device Notifier allows me to mount it without any kind of password! however, if any drive is mentioned in /etc/fstab, even if with the "user" option, it does require root-access! i.e. I can mount my other linux-filesystem as a regular user from commandline but neither through systemctl nor through KDE Device Notifier without giving any password! finally I have created files /etc/systemd/user/*.mount which allows for using "systemctl --user" to mount them oblivious of any root-access but neither KDE nor the mount-command are taking heed of this permission.
I'd like to put this mess into some order, get an overview which devices can and can't be mounted by users, and allow mounting by both scripted methods (KDE and systemd). I figured out, mount needs fstab, systemd needs changes in the related generator to truely be in sync with fstab. but what about KDE? how does KDE manage to mount anything that actually requires root-access on command-line, without asking for password nor using any kind of sudo? what sourcefile (I am on gentoo) do I need to change to grant access to stuff marked as "user" in /etc/fstab? and which kde-package would such a sourcefile be located in? and how do I hook into the method KDE used to get notified of new devices by a root-privilegued command-opportunity to mount my external drives on user-request?