your home trash directory MUST be available and defined.
Usually it's under ~/.Trash or ~/.local/share/Trash as default
you can echo $XDG_DATA_HOME to display it, if you get nothing, you can set >it by yourself.
First it is impossible to set something you cannot find in the first place.
Secondly env | grep XDG does not return any variable XDG_DATA_HOME, so that provided no help whatsoever. Thirdly, Google search on e.g. "where is linux Trash folder stored" does indeed turn up results -- namely this page and others like it. Search engines are source referrers, not source providers. If someone hasn't already posted it somewhere, it won't show in Google or anywhere else. Suggesting a Google search as an answer is not helpful.
So indeed, find / -iname trash will find it (recommend adding 2>/dev/null to eliminate all errors that will occur for inaccessible files), but novices have a lot of trouble with find's syntax.
So yes, it is usually ~/.Trash or ~/.local/share/Trash.
As for trash-cli, yes very helpful, but the correct instructions for it are:
sudo apt install trash-cli -y
alias rm=trash-put
alias rm >> ~/.bashrc ( or >> ~/.bash_aliases)
Now, I would like to know, if I set XDG_DATA_HOME to /tmp, will trashing a file move to /tmp instead? The concept of a Trash folder is great, but I'd like a little more sophistication like an Archive folder where I can archive-put little used files that I still want to keep but keep out of my main folder stash to eliminate clutter. I'm no linux novice, but I do have limited time--so that is why we collaborate--I save you time, you save me time!! I hope. Less is more, more or less.