I also get a 403 on the same page since they apparently block the entire Hetzner range (i had this IP for like 3 years and it is never used for abuse) (I sometimes use my machine as a shitty VPN since Turkish Goverment does site block with DPI). If they were using Cloudflare I could at least solve a Captcha and see the website
I try to check the forum post and found out that I was blocked by https://forum.palemoon.org , e.g., https://offline.palemoon.org/blocked/index.html . Don't know and haven't visited this site before.
https://www.palemoon.org works though.