I was successful upgrading.  Thanks for the Clues above.  For the benefit of someone looking for a how to upgrade to excalibur, the steps were:
1. Install current Devuan
2. sudo apt update
3. as root edit /etc/default/grub to uncomment os prober disable (or grub won't generate for other OS partitions)
3. sudo apt upgrade
3a. sudo apt install usrmerge
4. log out and restart
5. as root edit /etc/apt/sources.list to comment out current Devuan and add line from above for excalibur
deb http://deb.devuan.org/merged/ excalibur main contrib non-free non-free-firmware
6. sudo apt update
7. sudo apt upgrade
8. test
9. log out and restart

Its working...