I've worked out that the Sydney Linode DC dishes out IPs that were flagged in Spamhaus from April 12 to 14, which is right before I spun up a vps there to use for VPS on the 15th.
So its either that, or Porkbun in general, or the old in general... but they won't be specific because why you let a potential spammer know where they stuffed up, I guess.
The worst part is that XYZ just suspends the domain based on that automatically. It's just so frustrating.