I discovered awhile ago that so-called "junk bonds" are in fact very rewarding investments that are actually only risky by comparison to other bonds, and not by comparison to other popular asset classes like stocks. Been making $120/year off an $800 bond I bought that has grown in value to $950. Win!
Someone should brand junk bonds like they did with peer-to-peer lending. The latter was a bust (time and time again, I've read about the ills of P2P lending returns), but there could be a great dual-sided market opportunity for the former.
I can't say that I do-- I mostly learn about investment things by googling a question or a term and then reading all the results that come up and mentally aggregating what they have to say.
I will add that The Balance and Investopedia have been the leading sources of my education, all in all.