I raised the issue in PeakD Discord
How I see it. They probably don't consider Google's ranking too important. The blockchain means Peakd is doomed to be slowish and many frontends mean a significant part of the content on Peakd is doomed to be considered duplicate by Google.
You can ask AI about Google's search ranking algorithm, and you'll see the originality of content and website speed.
So they probably decided to emphasize user experience: Peakd is slow but cute and with many functions. Someone can say AI search will replace Google search one day so why even bother. Even if Peakd was superfast and had non-dublicate unique content, it would be hard to compete with so reputable site as Reddit.
Despite this, Peakd posts can be seen on Google. With links from Reddit (thanks to HivePosh), peakd posts have slightly better chances.
(This is only my opinion.)