I tried to build essentially the same thing on top of Matrix (and got rejected from YC in the process) - I haven't tried the app yet but I have some initial thoughts and questions. I really hope you succeed with this; forgive me if I come across as a skeptic.
#1 question: every notable social app had some clever strategy and/or shenanigans to attract a critical mass. What's your plan to tackle the network effect problem? Maybe 10% of the value of a social app is the UX, the other 90% is that the people I care about are there.
Are posts end-to-end encrypted, or encrypted at rest? Your video says E2EE but your landing page says encrypted at rest. There's no wiggle room for confused messaging on this. Your blog says you're using Matrix but one of your comments here suggests you abandoned that idea? If so, I'm curious to hear why. Are/were you sharing content directly in Matrix rooms, or storing encrypted content in an object store and using Matrix as a key sharing mechanism, or something else? Can you say more about the problems you encountered?
The landing page design is slick, but there's too much motion pulling my attention all over the place, and too many red flags. The animation for "Automatic Contacts" evokes a feeling that you're going to swallow up my address book and send unsolicited requests to my friends as soon as I sign up. The alarm bell with red dot is an anti-pattern. It feels weird to see all the other social networks I can integrate into my profile, considering this is squarely aimed at people who have rejected those other apps.
Your video says there are no ads, there never will be, and users are not the product. How, then, are you going to thrive in such an intensely competitive space?