There is a way to periodically blindly empty the trash on a Ubuntu 16.04 LTS system for a specific user.
Start with a script that contains the following lines:
#!/bin/bash rm -rf ~/.local/share/Trash/*
then use cron to have it run on a periodic basis.
(In fact, this works under Raspbian and other versions of Debian, also)
But what if it would be preferable to keep files for xx days, or until free space drops below yy, or some other parameter?
The question is in the title: How can I set up Ubuntu 16.04 to automatically empty the trash based on parameters?