Last post provided "the clue": problem with ubus authentication. Not due to luci revision change, but with openwrt/ubus revision change.
Note: change "support" to required user ID
Full solution:
- create support user with UID, GUID = 0 (for full access - change to taste)
- alter /usr/lib/lua/luci/controller/admin/index.lua to read:
"page.sysauth = {"root","support"}" from = "root"
-alter /usr/lib/lua/luci/controller/admin/servicectl.lua to read:
entry({"servicectl"}, alias("servicectl", "status")).sysauth = {"root","support"} from = "root" - NEW: add to /etc/config/rpcd:
config login
option username 'support'
option password '$p$support'
list read '*'
list write '*'
- may need to reboot
this may provide sufficient clues to get luci-app-multi-user wotking again, for anyone so inclined.