Powered on the Vero to continue the investigation, and the web UI responded with an authentication request as I believe it should, having modified /home/osmc/.config/transmission-daemon/settings.json Logs uploaded to pastebin using the uploader (uploaded everything, since I couldn’t see a specific ‘debug log’ option I’m afraid).
Still seeing two processes, the ‘double installation’ sounds like a good theory: going through my notes, I suspect the Debian version may have been installed whilst the builds were being discussed as a command line install, and then not removed when the app store version was published. So, I attempted to remove the Debian version sudo apt-get remove armv7-transmission-app-osmc, rebooted, and there are no instances of the service (My OSMC > Services shows no client available, let alone running/stopped). New logs uploaded.
App store > install Transmission client (and see in the progress messages that the package name matches above), reboot, and once again I’m getting two processes (My OSMC > Services shows the client running), with the web UI again giving a 403. Logs uploaded for a third time. Given that both processes appear to be installed by the single app-store request, and stopped by a single systemctl command, is it possible that the install is looking at two repositories, one of them being the jessie-devel repository mentioned in the testing thread? I’ve tried an uninstall & reinstall with the jessie-devel repository commented out of the sources list, and it doesn’t change the behaviour (still two processes, 403 in web ui), so is it possible there’s some residual elements of the double install when I try removing, either through command line or App Store?