Hello, fellas. In everyday usage, the subject and verb of an adjective clause (relative clause) precede a preposition. On the other hand, to make it more formal, the clause is used as the object of the preposition.
(More on relative clauses: https://englishtips4u.com/2011/11/08/engclass-relative-clause/ and https://englishtips4u.com/2011/11/09/engclass-relative-clause-2/)
According to Cambridge Advanced Learner’s Dictionary, a preposition is a word used before its object (a noun, a noun phrase, or a pronoun), connecting it to another word. It usually shows a temporal, spatial or logical relationship of its object to the rest of a sentence. Examples of prepositions are about, at, by, for, from in, on, through, to, with, and without.
(More on prepositions: https://englishtips4u.com/2011/09/17/engclass-prepositions/)
If the preposition is followed by the adjective clause, pronouns to use are only whom or which. It is never followed by that or who.
- He is the man whom we talk about.
He is the man about whom we talk.
- The lecturer whom you should listen to is explaining course materials.
The lecturer to whom you should listen is explaining course materials.
- The view which we look at is breath-taking.
The view at which we look is breath-taking.
- Surabaya is the city which I live in.
Surabaya is the city in which I live.
(in which has the same meaning as where)
Cambridge Advanced Learner’s Dictionary
Betty Schrampfer Azar, Understanding and Using English Grammar: Third Edition
Betty Schrampfer Azar, Fundamentals of English Grammar: Third Edition