Could you give a report of the statistics of the IP address in the DDOS attack? Maybe you can block all the ip address from China. As I known in China people have to use VPN to access some sensitive websites (such as 8964, falungong, dajiyuan).
One one hand they are abusing CDN or cloud platforms for their broken "collateral freedom" project
One the other hand, every effective DDOS protection outside China has been blocked by China already, like Google Project Shield, Cloudflare, etc.
Very few S3 CDN IP address left with 443 port open, so greatfire.org carefully picked those and hosting content mirrors there.
Although what they operate is totally free speech, legal and reasonable, but it's like your bad neighbor in a VPS who eats all your co-hosting CPU, bandwidth and disk IO. You have no choice but move to somewhere else.