There was a change a while back that made the front page less volatile, around that time you started seeing stories merged more often, and traditional news creeping in a bit more. I think it is sort of like a lightning rod to keep the rest of the front page pure. Before that stories would show up and get flagged constantly, and the front page would change multiple times an hour.
One thing that I have noticed is that 2020 was a bit of an eternal september for hn. Many times I see people posting things that don't really seem to work with the hn style, but they have a fairly high karma count and an account that was created in or after 2020. I think maybe a bunch of people suddenly working from home felt safe to use the internet without a boss over their shoulder, and needed a bit of community they were missing from not going in the office. This influx has watered down the ability of hn to aggressively flag/downvote politics, dumb jokes, etc.
Though, all in all it's still mostly the same it has been in the last 10 years or so.
I hadn't connected that to a pandemic-induced demand increase, but that could well be true.
As for submissions (rather than comments), it does feel like HN has shifted more towards broader industry and politics news, rather than just tech and programming. I'm okay with this, in fact HN has displaced Reddit for me thanks to the much higher standard of discourse, although I do worry a bit about marginalizing the crunchy tech content for those who come here for that.
I think the guidelines might be right, in that this hasn't really seemed to change in the ~10 years I've been here.