Lemmy is very “open” right now; some might say by design, other might say flawed. OP is maybe coming from a good place and actually wants to help, but instead of doing it tactfully, OP is becoming the exact thing they’re advocating against — a spammer posting garbage.
I am new to the fediverse, and I don't use Friendica, so I could be entirely wrong about this. However, from what is described, perhaps Friendica has some sort of feature in which would trigger your instance to go out to fetch some data from another instance. Someone exploited this feature, spammed your instance with content from assortment of subdomains on the *.activitypub-troll.cf domain, and most if not all of them are probably non-existent. As result of that, your server is re-checking every 10 minutes to see if they've came back online. This would also explain why shutting down the Friendica service resolved the problem for you.
Are there ways to manage lists of such? For example, on the former platform that doesn't deserve a call out, you can do "me_irl+meirl" and aggregate both into one feed. This makes reading the (albeit potentially cross posted) content in a unified feed much easier.
Another similar point I'm having a hard time getting over is that with a centralized platform, it is easy to go to "Subject A", and see everything on that subject. However, now I need to see "Subject A@lemmy.world", "Subject A@lemmy.ml", "Subject A@someother.instance"... Yes, I could subscribe to them all, but this ultimately end up creating a noisy home feed with also "Subject B@lemmy.world", "Subject B@lemmy.ml", "Subject C@lemmy.world", "Subject D@lemmy.ca", ... etc. all baked into one feed, as opposed to just something focused on "Subject A".
Lastly, discoverability leaves a lot of room for desire. Today, I'm fairly new to Lemmy, I am actively seeking out communities that I might be interested in, across multiple popular instances, and hoping that federation is enabled between the two instances. Tomorrow, I'd find that I'm subscribed to too many (see the noisy main feed issue above), and I'd remove a bunch. Next week, am I likely to go to the Join Lemmy directory to find new instances, and add "duplicate" communities from newly popular instances? I think not.
I think the long term survival of the platform (to expand beyond just us tech nerds that hate the former platform) will depend a lot on streamlining this workflow to make content discovery much more consistent. Even a simple option where a pseudo "!Community@" (with no instance) feed that aggregates all the "!Community" regardless of instance that you've subscribed to, might go a long way.
Yeah, the entire setup is quite finicky still. Part of me thinks Fediverse is forced into the spotlight by Twitter (Mastadon) and Reddit (Lemmy), and the whole thing is not quite baked yet. Don't get me wrong, having a more open space is great, but there are so many things that's not quite ready for prime time. I hope the dev team behind the platform (not the self hosted instance admins) will be more open to ideas and rapidly improve the platform.
This right here.
Op, if you’re not ready to moderate, don’t spin up your own server or do your own private instance. If you’re going to moderate, do it properly and don’t spew bad ideas while hiding behind a dumb “alert” throwaway.