Listing Unavailable Media

Had a bit of a data problem and had to recover from backups so I need to somehow generate a list of missing media.

Advanced filters in Libraries to show Trash=True doesn't work, showing zero titles, even if I know there's media marked as Unavailable.

WebTools-ng isn't a workable solution (as far as I have been able to test): The built-in csv search and export preset only works for TV, not Movies; doesn't seem to work for large libraries (counts as it goes through media and then just stops part way through); and even when it does work, over half the time results in a csv with ERROR in every field.

I don't mind getting into the weeds of sqllite. I've looked through the library.db before. I've made a copy and looked through again, but can't find any relevant availability columns, or anything that seems related. If anyone else knows different, please let me know!

In short, any reliable way of doing a one-off Unavailable export?