I have seen 2 answers in stackoverflow:
A "trivial" property is one that holds either for all languages or for none.
The property is trivial if it contains every TM, or if it is empty.
My problem is: Saying that a property is trivial if it contains every TM is not the same as saying that a property is trivial if it contain all the languages (including non RE
languages).
Same as for: Saying that a property is trivial if it is does not contain any TM languages is not the same as saying that a property is trivial if it is empty.