Thanks for that, now solved. Assumptions confirmed BTW.
 
As I had been using Ascii day-to-day until now (I had only installed Chimaera experimentally) I had not previously encountered the new need to add a dash suffix to the su command to get root's environment settings, and hence get the system apps in the path.  I fail to see the point of this change, but still ...

I also needed to enable os-prober in grub (for the benefit of other readers, the file /etc/default/grub), by uncommenting the existing "false" line :

# If your computer has multiple operating systems installed, then you
# probably want to run os-prober. However, if your computer is a host
# for guest OSes installed via LVM or raw disk devices, running
# os-prober can cause damage to those guest OSes as it mounts
# filesystems to look for things.
GRUB_DISABLE_OS_PROBER=false

Shame that update-grub interpreted my DOS FAT partition as a Windows7 installation, but I guess you can't have everything, and I suppose I could change the name if I edited /boot/grub/grub.cfg, despite the dire warning at the top not to do so.

Kye ( www.kye.me.uk  )  A puzzle game with hundreds of levels (+ design your own). There is a Python version for Linux. This website explains it, but for the Python Kye download, follow link from its Links page.

PRBoom ( https://sourceforge.net/projects/prboom/ ) A port of Doom, with a Linux version

Soma ( https://www.somagame.com/ ) Available for Linux, Mac and Windows

OK :-

[root@mesh-devuan:~] # mount -t ntfs-3g /dev/sdb2 /mnt/windows/
ntfs-3g: Failed to access volume '/dev/sdb2': No such file or directory

ntfs-3g 2014.2.15AR.2 integrated FUSE 28 - Third Generation NTFS Driver
                Configuration type 7, XATTRS are on, POSIX ACLS are on

Copyright (C) 2005-2007 Yura Pakhuchiy
Copyright (C) 2006-2009 Szabolcs Szakacsits
Copyright (C) 2007-2014 Jean-Pierre Andre
Copyright (C) 2009 Erik Larsson

Usage:    ntfs-3g [-o option[,...]] <device|image_file> <mount_point>

Options:  ro (read-only mount), windows_names, uid=, gid=,
          umask=, fmask=, dmask=, streams_interface=.
          Please see the details in the manual (type: man ntfs-3g).

Example: ntfs-3g /dev/sda1 /mnt/windows

News, support and information:  http://tuxera.com

FWIW I get exactly the same result with  mount -t ntfs-3g /dev/sdb2 /mnt/windows/  and ntfs-3g /dev/sdb2 /mnt/windows/

blkid shows info about the other drives but sdb does not appear at all.

This is ASCII and ntfs-3g is installed.  It would seem the problem is with non-recognition of the partitions' existence and it does not even get as far as trying to read the file system.  I'm wondering if partitions created in Windows have a different indexing or header or something, which is why Linux does not recognise them. It is an older mother board without UEFI.

sdd1 and sdd2 are vfat partitions and they can be mounted with no problem in Linux.

I was puzzled by this screen too. For a moment I thought that Devuan had developed its own graphical desktop environment [DE]! But I took it to mean that the top tick box meant whether you wanted a graphical DE or not, and the next five chose which specific type of DE you wanted. So I ticked the top box and also KDE, with the other four DE boxes blank - that worked for me.

It seemed to me that the top box was redundant because if you ticked one of the five specific DEs then of course you wanted a DE.  The five specific DE lines might have been indented like subheadings. I don't know what would happen if you ticked one of the five DEs but not the top box :-S

That's how I interpreted it - does anyone kow better?

@ fsmithred : Thanks for that, I get it now.

I have just installed ASCII and I don't recognise some of the reviewer's complaints. 

I chose the expert non-graphical install from DVD, and it went smoothly except it said I had an EFI motherboard and I should put GRUB on a USB stick. However I don't have an EFI motherboard so I ignored it, with no repercussions.

I used Debian before I used Devuan, and it seemed to me that the installation procedures were practically identical : has this guy never installed Debian?  I once did a net install of Debian and it did take hours (literally, waiting for packages to be downloaded) and would never try that again, Debian or Devuan.

He was installing on a VM, so he had graphics problems.  I have rarely managed to install anything on a VM without graphics problems and I usually just give up and have to accept a shrunken a 800x600 (or whatever) subscreen.

I was not asked to set up partitions manually; the option was only offered (and I took it). It also offered to make partition decisions itself, even in this "custom" installation - I don't know what it would do with that option.

He seemed to find the account set-up stage confusing.  I was simply asked to set up a root account and then a user account. I never like the sudo method of doing admin (AFAIR Ubuntu insists on it). I find when I need to do admin tasks that I am doing them for a little while, so I don't want to have to keep adding "sudo" in front of every command.