I have used this Add-on intermittently for years, and it has really worked well and is so easy to use, but inconsiderately did not make a financial contribution (which is unforgivable, really. It's because I don't keep good track of these things).
I've just now tried to download a video as an .mp3, but encountered an error, related to the changes in how YouTube is working. From the developer site, I found that they now now have to use an intermediate server, and their operating expenses have increased. So I was happy to take the opportunity to make a donation for the "Pro" version, and now the downloads work perfectly and as easily as before. Thanks so much to Dishita for making this service available. I try to respect artists as well, but sometimes special needs arise.
I am sorry to see that there are some "angry" users, who seem to take great personal offense about the changes taking place in YouTube, and seem to have no sympathy toward the Developer. I'm sure it takes time and much effort to make the required updates, and I wish people would be more sympathetic, empathetic, more considerate, and LESS ANGRY. We all pay a price for that.