The rule against ending sentences with prepositions is a good example of unwarranted prescriptivism. Those who invented it were insufficiently knowledgeable about the history of English as a Germanic language. The term preposition ("a preposed word") itself is only a general description. The rule was influenced by grammatical theory based on Latin--and English is not Latin...But careful writers, aware that the "rule" still has many supporters, try to avoid "trouble." But "from where are they?" is not natural English!...In highly colloquial French, one hears "c'est la fille qu'il sort avec..." 'She's the girl he goes out with', as opposed to "c'est la fille avec qui il sort."
That is not and has never been a rule. Multiple academic sources support this contention. Here is one: https://www.merriam-webster.com/words-at-play/prepositions-ending-a-sentence-with Still, a very funny episode from the old TV series Designing Women went something like this: at a high society function the main character asked a lady, “where are y’all from”? The lady stuck her nose in the air and said, “I’m from where we don’t end a sentence with a preposition”. The questioner rephrased with, “Oh, where are y’all from b****?”