Not only have I created a openSUSE Feature request that no one reads about adding a Trash Bin icon to replace the red folder.
It is still missing from the Breeze icons.

I have talked about this 'till I was blue in the face. I'm not a developer but I have been compiling the kde source code since Mandrake 7 in the year 2000.
Every version of kde had a Trash Bin. I even contributed to the Plasma 5 survey.

The Visual Design Group refused to add it to Dolphin.

I know this thread is old, but it's about the 1st one I came across when researching how to make the usual desktop icons appear on the account that I imported into a fresh Devuan Beowulf install.

I've been testing most of the current DEs with this install and account, and they all seem to have an option somewhere to select which of the standard icons you want to have appear on your desktop, including the trash but also mounted external drives.

I can't find anything in KDE that does that, which seems like a big obstacle for people coming from Mac or MSWin...

Kubuntu 20.04 and 20.10 have the same problem: There is no Trash bin on the desktop.
I think 18.04 also had the same issue.
I don't know why they don't put a Right click- > Show Trans Bin

So, what you need to do is get on the web and search for user manuals and topics. In case no one can tell, I am against this kind of design.

THIS IS THE SOLUTION:
Right-click the desktop and select "Create New->Link to Location (URL)..." and put in "trash:/" for the location.