As far as i know, Transitive verb can only become passive
Look at this example
The mangers talked about the problem.
The problem was talked about.
As far as i am concerned, when a preposition isn’t part of the verb (phrasal verb), the verb cannot become passive because it loses the feature of transitivity.
The preposition About in the sentence doesn’t form a phrasal verb with talk; however, it can come in a passive form.
How can talk about come in a passive form?