Here are some recommended secondary domain names:
- https://ydns.io/
Demo: http://wangbin.ydns.eu/ - https://customer.l53.net/ (If you can apply for it, it's quite good, renewed for a year, free, can be bound to cf)
Demo: http://xixiku.ggff.net - https://freedns.afraid.org/ (Ten thousand level domains, apply freely)
Demo: http://langniao.3n.cc and http://langniao.k.vu - http://ym.aiygo.fun/
Demo: None available at the moment - https://hzyo.cn/ (Heard it has been taken down)
Demo: http://langniao.zxzi.cn - https://www.cloudns.net
Demo: None available at the moment
If there are others, please send them to me, and I'll compile a list, preferably with demos.