This is exactly it. I freaked out that I had done something wrong until I thought to try turning Private Relay off!
For those that may not be aware, the latest version of Safari (on both iPhone and Mac) includes a feature called Private Relay, if it's turned on it masks your real IP address with a different one, like what a VPN does as Steve said. The problem that arises is the "fake" IP that this assigns to you, or the range of addresses it assigns from, could also be used by countless other people so it can appear to some websites that unique individual users are all logging in from the same computer or connection point. Thus, the system gets ban-happy on those IP addresses.
Anyone having this issue on Safari, I would suggest turning off the Private Relay feature (if on a Mac, open Safari preferences -> Privacy -> Hide IP Address) in order to access Disboards, at least until the admin team are able to figure something out.