I don’t know what counts as legitimate sources. I’ll let the professionals figure that one out.
> Should advertisers be banned from sponsoring journals or conferences?
It baffles me that you apparently think this is some kind of zinger. Yes!
Got it. So you want attention to be controlled by the whims of academic/government/publishing bureaucrats or black-box ranking algorithms who are the arbitrators of legitimacy. I can't say I agree with that opinion, but different strokes for different folks.
Journals less commonly but pretty much every conference out there of any scope is sponsored by companies. In fact, absent sponsors, very few conferences would exist other than small volunteer-run ones.