Here's a workaround that will yield untagged items. Works on platforms that have a command line interface where the jq tool is available (e.g. MacOS, Windows, Linux). The following is what I did in a MacOS zsh terminal to find my untagged items. I happen to have jq version 1.6 installed.
Install the jq command line tool if you don't already have it installed (https://jqlang.github.io/jq)
File/Export in Enpass
Select .json format, let's say you put it in a file called items.json
In a command shell, cd to the directory where items.json appears
Run the following command (note that if you're using a different shell, the syntax for the stuff outside the jq command might vary a bit:
cat items.json | jq '.items[] | { title, folders } | if .folders != null then del(.) else . end | .title ' | grep -v '^null$'
This will yield a list of item titles -- but not just any old item titles, it'll be only those that have no tags. :-)
And don't forget to delete items.json after you're done! There's lots of sensitive information in there that is exposed while the file exists.