I installed arch to a VM yesterday for some stuff and for the life of me I couldn't figure out why I couldn't get Paru or Yay going and well...there ya have it. spent like an hour trying to figure out why they both weren't working.

Nobody has been claiming responsibility. Some of the AUR forum peoples think it's butthurt malware devs who got caught uploading malware, but it's just a shot in the dark.

https://status.archlinux.org/

Been on and off for months now.

Services I know that have both HTTPS and SSH access have seen all sorts of weird stuff seemingly related to LLM bot scraping over the past few months. Enough to bring down some git servers.

You could donate to the project but I don't think a mirror would help.

Mirrors still see a specific instance as the truth and sync to that. A mirror would make it possible for someone to download an update from you while the truth instance is down (or always from you if you're closer and faster) but without that first truth instance there'll be no new updates. There won't be syncing across mirrors. And it wouldn't really impact any DDOS because it's still that first instance being targeted.

DDOS mitigation can take one of two main ways. Add enough server power to overcome the DDOS, this is insanely expensive and out of each for most all but like Amazon and Meta. The second is to cut off whatever is doing the DDOS, either by disabling the specifically protocol or endpoint being used or not allowing certain IPs to connect. These are probably what they are doing already and there's not much you can do as an outsider to help with this either sadly.