I would imagine one post preview with a very compact list of instances on which the posts were posted so that you can enter either of those posts' view.
Or merge the posts into one view, show somehow it's a merged post, and merge comments as well (and let you choose the instance on which you want to comment if you create a new top-level comment).
Reddit had similar issue but it wasn't that bad since you hardly ever had 2-4 similar communities - something that appears to be very common with decentralised lemmy.
Good start! But to be able to "sell" it (i.e. make users use it) you gotta say how it's this better/different from alternatives like yt-dlp or youtube-dl?
Why do you need a browser on a PC to install new OS on your phone?