Hey! That's (almost) me!
My desktop has been Linux for multiple decades.
I buy paper notebooks and write with pen. Always have.
mp3 player: You got me on that one. Although I did buy a Yoto (https://us.yotoplay.com/) and perhaps I should just use it as an mp3 player, but to be honest it's a poor player (no shuffle without app, etc). On the flip side, what I like about it is putting podcasts on cards. I can assign a card to any podcast feed and it will let me choose which episode to listen to.
DVD library: Nah - I used to have one and gave in to Plex. I don't know how many of my 20 year old DVDs will work now. Video files have more longevity. But someone did once post on HN how he had set up a physical card + NFC for his kids. A given card has a particular movie/TV show. They insert the card, and the TV plays just the movie on the card and turns off after. I'd definitely pay for that if I could buy it. I'm sure many parents would.
Disc rot seems way overblown it seems, at least for DVDs. LaserDisc does have this problem, though.
But what he’s onto is the thing that unifies all these weird little niches: they’re motivated by a bone deep annoyance with the most popular big tech offerings. None of these groups are all that big, but if you add them together there’s something here.