Real reason for the hate: The Linux community is overly focused on tribalism and has a console-wars mindset where what I'm using is obviously the best and everything else must be flawed and terrible. Manjaro is probably fine for most use cases.

...although I'd still suggest just using base Arch instead. :)

One distro that I've recently found runs pretty well on older/slower systems like this is wattOS. It's a distro focused on power efficiency, but because of that it does well on underpowered systems.

I think having a noscript site like old.lemmy.sdf.org available could only be a net positive, I can't imagine that it would hurt to have it as an option, as long as it's not too much work to keep it running.

I agree with these other two posters. Why not wait and see what Threads even ends up doing before they're potentially defederated? Obviously, Meta wants to find some way to make money from the Fediverse, but will it actually affect users who aren't registered on their servers? Let's see.