I could ask this question on askubuntu or stackoverflow or any other similar site, but I figured some people on TeX.SE will have had the same problem, so here goes.
I uninstalled TL2017, following this much acclaimed checklist. I did an additional system wide search for texmf and texlive and some other terms, found some more files, deleted the ones not used any more. I did
$ which tlmgr
$ which pdflatex
$ which latex
Which all returned nothing, so that's good. Two things remain.
One of them is shown in the picture below. I don't know how to eliminate the handy texlive icon from unity search. Needless to say, when I click it, nothing happens. I don't know where to find the setting that will remove it. I know it's in a directory containing a bunch of files that start with [desktop], but I can't seem to lay my hand on it. If I found the directory, I could just delete the file. It could be so easy!

/usr/share/applicationswhere it could be located. – Henri Menke May 02 '18 at 02:05