You have Churches advertising on the radio and TV all the time. Think of billboards you have seen, with spiritual messages or advertising churches. Those are secular media.
I worked for a Christian charity that ran infomercials on how to use gift annuities for estate finanical planning on TV.
There is absolutely no prohibition on tax exempt organizations advertising. The only thing they can’t do is cross the polical line and start endorsing particular candidates or campaigning against particular candidates. They can campaign for political “issues” all they want.
I haven’t noticed this stuff because 1) I don’t see any billboards where I live—they may be illegal here, 2) I never watch TV, 3) I don’t read newspapers, 4) about the only radio station I listen to is Christian, commercial-free, and listener-supported; although there are what could be called quasi-commercials on it. About all I remember of Christian advertising is the “Jesus Saves” billboards I used to see years ago in the South.