So apparently Apple removed support for the Network Trash Folder in AFP 3 or something a long time ago, which is why it is documented as no longer working.
Samba has a recycling bin module which isn't quite the same as a proper trash, but is better than nothing. When a file is deleted, it is moved it into a special directory where it can be manually deleted permanently later.
Since Apple dropped trash bins over AFP, I was hoping to find a similar feature in Netatalk, but no luck. Any chance such a feature might be considered? I would consider adding it myself, though I might need guidance on where to find the relevant code to hook into.