Peertube is a great platform. And it has its uses. But it will never compete with YouTube - YouTube’s business model actively incentivises and pays people to post media to their platform.
Peertube is more likely to be to be the opposite - donation run, and given videos are exponentially more expensive to host, it’s highly unlikely that creators will receive any compensation for their work. In fact it’s more likely theyl be in the list of people donating to the platform (or they’ll own the platform outright)
While this might be fine if a creator makes the majority of its money elsewhere, via patreon or sponsors or whatever, it’s not going to work out for any aspiring or up and coming YouTube who has yet to become big enough to start diversifying their income base.
Except I’m dead certain you can buy screens a lot larger than 4.2 inches - the 6 inch screen behind the Kobo Clara HD is actually all over AliExpress and eBay, and it has a backlight and is not marketed for as a replacement for the eReader. Kobo just glues a thin metal plate and a battery to it for rigidity, but otherwise it’s identical. And there are a fair number of other screens you can find online in various sizes if you want to get them working.
The hard part is getting data sheets or reverse engineering them. But it’s far from impossible.