GKP says "whom" is "rarely used these days except after prepositions". Really?
I don't know how to use the various corpora that could be consulted to determine the point, but I for one use bare "whom" quite readily in relative (but not interrogative) clauses. E.g.That woman with long red hair whom we saw at the supermarket this morning, I saw her again this afternoon at the beach.Who did you ask to see, Mr Jones or Miss Smith?
In non-professional writing on the internet the choice between who and whom is made by rolling dice. The distinction is lost except among language aficionados
but I for one use bare "whom" quite readily
And no doubt you will continue to do so while the word drops out of general usage. I know how to use it but generally avoid it so as to not sound excessively posh."Whom" won't be missed. And for a large part of the population is already not missed.