Or you just put the apk behind a big obvious button saying "Advanced users" and a checkbox for users to affirm they are comfortable installing/working with APKs

Or you just put the apk behind a big obvious button saying "Advanced users" and a checkbox for users to affirm they are comfortable installing/working with APKs themselves, which is required before the download can start. You might still get the questions but at least then support teams can legitimately say that kind of advice is not provided as the users agreed to handle such matters.