One of the reasons I'm not a huge fan of old.slrpnk.net is that I can't figure out how to access content from other instances.
old.slrpnk.net should still have posts from other instances, as far as I can tell. They only show local stuff by default, so you have to set “listing” to “all” to see them (the small toggle under the yellow tagline). If you want to primarily interact with posts from other instances, lemmy.today is probably the better choice though either way. slrpnk.net looks like it mostly focuses on local communities.
I have noscript running and I have cloudlflare blocked.
The good thing about mlmym (the software behind old.lemmy.today, old.lemmy.world, and so on) is that it's entirely usable without JavaScript :)
So as long as there isn't something like cloudflare in the way that does require JS, it should work fine to use it that way.
Looking at it right now though, @mrmanager@lemmy.today it looks like old.lemmy.today is erroring with 502?