Don’t know how much of you seen this, but the last two days there was a “digital event” called the Hifi Summit, made by some YouTubers such as Techno Dad and Joe’n Tell. I couldn’t see all the videos but seen some and they are very interesting. Now beware: there is a lot of “ad like” presentation, but the two I’ve seen about HDMI 2.1 and Vantoo founder on speaker project are very nice in the technical, at least IMO.
Also, since they are on youtube, they are free sooo… why not? Anyways, this is a little less focused on headphones, but as an Engineer and Audio enthusiast, I really liked the discussions they had. The videos have about 40min to 1h and you can mostly hear then on the background.