Finally I got time to replace my old braindead isp branded Huawei lte router with a fine Teltonika one. So now I can open ipv6 ports in too. :)
2:221/1 aka 2:221/0 is now answering (binkp) at native address: 2001:999:93:8ad1:f1d0:2:221:1. The negative thing is that the address is dynamic. I need to set up dyn updater later.