522 error - trying to host on android phone termux nginx mobile connection with ipv6

Hopefully you have the SSL certificate at your host/origin.

Moreover, regarding the compatible ports (8080 is compatible) you can see the list here:
https://support.cloudflare.com/hc/en-us/articles/200169156-Identifying-network-ports-compatible-with-Cloudflare-s-proxy

Also to note here about firewall, maybe you would need to add Cloudflare IP addresses and allow Cloudflare to connnect to your host/origin server?

https://support.cloudflare.com/hc/en-us/articles/115003011431-Troubleshooting-Cloudflare-5XX-errors#522error

You mean you put :orange: to :grey: for the AAAA records or something other like Page Rules, etc.?