I apologize for the slow access to forum for Chinese based users. This has been a known issue at FreeFlarum that I haven’t had time to properly resolve yet, unfortunately. This will be looked at in the future though (I assume during this summer). For now, the Cloudflare proxy for all forums that is being used by FreeFlarum was an attempt to mitigate the slowness of the loading times for Chinese visitors, however that did not have the desired effect of visibly speeding up the load times. An alternative approach will be required, one that I am not yet fully aware of. Thank you for the link to the possible solution though - I will study it in more detail later. I think it will provide me with some inspiration on how to tackle this issue.
html5syt Is there have other ways to increase speed in China? Such as something in Cloudflare Pro or up?
I have heard that Cloudflare has some services that can speed up your website, but because FreeFlarum is a free and community provided service maintained in my spare time, it is unfortunately not possible for FreeFlarum to operate outside the Free tier that Cloudflare currently provides.
An individual forum might be able to properly point its domain towards the Cloudflare nameservers and utilize the services available in their paid tiers, however I have never had experience with these services, so I can’t tell if they will actually help you speed up your forum. I strongly recommend you to discuss this particular thing with Cloudflare’s support before paying for something you wouldn’t need in the end.
html5syt Second, Is the “custom domain” uses ssl-tls/custom-hostnames in Cloudflare? If yes, why I can’t use my way?
The SSL certificates are obtained by FreeFlarum through third-party certificate management services, such as Let’s Encrypt and ZeroSSL (through the Caddy webserver), after you successfully link your custom domain to FreeFlarum. This process is automatic and should yield valid certificate, if the necessary conditions are met.
Your custom domain seems to be set up properly, and the SSL certificate seems to be valid. If you are perhaps asking whether you can use your own SSL certificate instead, then this is unfortunately not possible at FreeFlarum at the moment, and there are no plans to implement such feature in the near future.