As Admiral Pat mentions, embeds are easy enough. I don't know how Tesseract does it, but a low-tech solution is to just replace 'watch' in the URL with 'embed' and stick it in a iframe. From Lemmy's GitHub, it looks like there's been work on this, but I'm not familiar enough with it to know whether it's for future versions that haven't been released yet.

New videos used to come in to Lemmy as expected. There's been some regression that stopped it. It's possible to bring them in manually though (by searching for the URL), and - like with embeds - it's possible that it's been fixed but not yet released.

PT's videos channels are ActivityPub Group types like Lemmy's communities, but it doesn't handle federation the same way. It does it in a way that's more compatible with Mastodon. Lemmy's communities Announce everything they receive (posts, comments, votes, etc) and so if you receive that Announce, then as long as you trust the community, you can trust that the contents haven't been changed and process it. PT's video channels only Announce new posts (so on Mastodon, it appears as if the channel has Boosted content by the channel owner), but for everything else, it's a combination of sending out a 'post update' (which is essentially an invitation to query the outboxes it provides for votes and comments), and just flinging out the comment as is, without the HTTP signature. If you get that comment, then you can either use the LD signature that Mastodon includes to verify, or you can look at the ID, and fetch it from it's source. As such, Lemmy's federation model is mostly Push-based, whereas PeerTube's is a bit of Push, and a lot more Pull.

No - not particularly.

I don't doubt that they have some gut level opposition to the other things, but I don't think they'd care enough to force a potential government shutdown the week before Christmas or threaten to spend however many millions it'll take to primary Republicans who won't come on board if it wasn't for the debt ceiling.

It's very simple - Trump's been lying all along about cutting spending, and he's trying to avoid having to get the debt ceiling raised by the next congress while he's in office and he'll be the one signing the bill. He's counting on his supporters'dull wits and short attention spans to stop them from paying too much attention to the fact that he's pushing to raise it now, Later on, he'll be able to say that it had nothing to do with him because it was passed by the previous congress and signed by Biden, and the dunderheads will just nod and go along with it.

The rest is diversion, meant specifically so that allied media can run articles like this one, in which they gloss over the debt ceiling (if they mention it at all) and instead talk about the sorts of things that will get Jim Bob Bigot's jockeys in a twist.