Many thanks, chewitt!
I browsed the Kodi log and all looked good. Used systemctl to check on system status but could not find why SSH / SFTP not working.
Despite changing UEFI "Core C6 Mode" to disabled, many softlock error messages occurred while systemctl was waiting for my response.
My HTPC AMD A10-7800 build is 7+ years old and is not playing nice with 10.0.2. However, I expect some AMD Ryzen builds could experience the same softlock issue.
I will wait for early winter (when I have more time) to see if anything has changed with the latest LibreELEC but I expect the problem will persist. Looks to me that to go forward I will need a new Intel build that is known to run well with LibreELEC.
Just a note for anyone going forward to Kodi 19 from 18 and thinking they can fall back easily using Backup / Restore, I found that after re-installing LibreELEC 9.0.2 that Backup /Restore would not install properly from the Team Kodi repo.
My solution was to unzip the backup file on my Windows PC, and FTP over to my HTPC the following: script.xbmcbackup, it's addon data, and the eleven script.module.xxxx files that are prerequisite for Backup / Restore. After a reboot I was able to use Restore to recover my previous system with the exception of a few settings.