Cell phone detected but cannot be mounted

My old Samsung cell phone has the usual internal flash card, which is freely accessible through its USB/charging cable to Windows 7, but in keeping with recent revelations about Windows 10 I'd rather download its pictures/video with a GNU/linux application.

Here's what I've found out so far:

On first plugging the USB cable into the live cell phone, I get this dmseg output:

dmesg | tail -n 12
[27233.803901] sd 7:0:0:1: [sdc] Write Protect is off
[27233.803953] sd 7:0:0:1: [sdc] Mode Sense: 0f 0e 00 00
[27233.808208] sd 7:0:0:1: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[27233.809155] sdb: sdb1
[27233.815065] sdc: sdc1
[27233.819345] sd 7:0:0:0: [sdb] Attached SCSI removable disk
[27233.829468] sd 7:0:0:1: [sdc] Attached SCSI removable disk
[27234.006643] sd 7:0:0:0: [sdb] Synchronizing SCSI cache
[27234.009855] scsi 7:0:0:0: rejecting I/O to offline device
[27234.009858] scsi 7:0:0:0: killing request
[27234.037647] sd 7:0:0:1: [sdc] Synchronizing SCSI cache
[27521.602474] systemd-hostnamed[9305]: Warning: nss-myhostname is not installed.
Changing the local hostname might make it unresolveable. Please install nss-myhostname!

A little research reveals that the correct Trisquel package is libnss-myhostname:

sudo apt-get install libnss-myhostname
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
libnss-myhostname
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 14.6 kB of archives.
After this operation, 61.4 kB of additional disk space will be used.
Get:1 http://us.archive.trisquel.info/trisquel/ belenos/main libnss-myhostname amd64 0.3-6 [14.6 kB]
Fetched 14.6 kB in 0s (33.5 kB/s)
Selecting previously unselected package libnss-myhostname:amd64.
(Reading database ... 520376 files and directories currently installed.)
Preparing to unpack .../libnss-myhostname_0.3-6_amd64.deb ...
Unpacking libnss-myhostname:amd64 (0.3-6) ...
Setting up libnss-myhostname:amd64 (0.3-6) ...
First installation detected...
Checking NSS setup...
Processing triggers for libc-bin (2.19-0ubuntu6.6) ...

Trying the let's-plug-it-in-and-see-what-happens routine:

[28459.310167] usb 1-1.1: new high-speed USB device number 21 using ehci-pci
[28459.398454] usb 1-1.1: New USB device found, idVendor=04e8, idProduct=6640
[28459.398465] usb 1-1.1: New USB device strings: Mfr=3, Product=2, SerialNumber=0
[28459.398470] usb 1-1.1: Product: OEMSAMSUNG_Brew_SCH-U680
[28459.398475] usb 1-1.1: Manufacturer: SAMSUNG Electronics Co.,Ltd.
[28459.400626] cdc_acm 1-1.1:1.0: ttyACM0: USB ACM device

At least,now my Lenovo T420 knows what has just been attached to it, but Trisquel 7 hasn't let it be listed as a device.

On plugging the cell phone in to the USB cable I get:

dmesg | tail -n 12
[30194.088749] sd 9:0:0:1: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[30194.093998] sdb: sdb1
[30194.101157] sdc: sdc1
[30194.107643] sd 9:0:0:0: [sdb] Attached SCSI removable disk
[30194.112892] sd 9:0:0:1: [sdc] Attached SCSI removable disk
[30194.115215] sd 9:0:0:0: [sdb] Synchronizing SCSI cache
[30194.121814] systemd-udevd[10123]: inotify_add_watch(6, /dev/sdb, 10) failed: No such file or directory
[30194.134650] sd 9:0:0:1: [sdc] Synchronizing SCSI cache
[30194.174870] systemd-udevd[10123]: inotify_add_watch(6, /dev/sdb1, 10) failed: No such file or directory
[30194.178023] systemd-udevd[10126]: Failed to apply ACL on /dev/sr1: No such file or directory
[30194.178033] systemd-udevd[10126]: Failed to apply ACL on /dev/sr1: No such file or directory
[30194.298498] systemd-udevd[10123]: inotify_add_watch(6, /dev/sdc1, 10) failed: No such file or directory

ls: cannot access /dev/sdc*: No such file or directory
george@george-ThinkPad-T420:~$ sudo ls /dev/sdb*
ls: cannot access /dev/sdb*: No such file or directory

sudo ls /dev/sr*
/dev/sr0

sudo mount /dev/sr0 /mnt/usb
mount: no medium found on /dev/sr0

Note that there isn't any /dev/sr1

What's my next move ?