Just to update this in case anyone stumbles across it…
I just changed phones again, was now faced with (once again) rebuilding all my “smart albums” on the new phone and tripped over a entry in the forum that referred to a backup/restore process in the Albums menu.
Sure enough, if you open up Albums and then open the menu (upper right corner in current version), there is now an option to backup and restore albums!
Great – I simply backed them up on the old phone, transferred the backup file to the new phone, restored them on the new phone.
Worked great, all my smart albums were back in place within a minute or two!