I'm a regular HN reader, yet I've never heard of half of these. This doesn't sound like the kind of stack you'd want to adopt if you ever want anybody else to work on the code.
However, I don't think the technologies he/she mentioned are little known. Scala, Akka and TypeScript are certainly well known. The last I heard, Vue was based on a fork of Snabbdom.
BTW, it may be worth notice that the code base of Lichess.org also uses Mithril. I used Vue in the past but converted my choice to Mithril afterwards. To me, Mithril is simpler to learn or use. My code using it is cleaner and easier to maintain. But this is certainly anecdotal and YMMV.
Scala, Akka, TypeScript, React...uh, where have you been?
Lichess is an impressive project, their chess app is not only excellent compared to everything else out there, it's incredibly efficient, and handles a ton of traffic with ease. I don't think the creators chose the stack without reason.
This is probably not the go-to stack but not for the reasons you've stated.