Reading Why isn't there any such option - middle-relay behind NAT? it seems there are (were?) no way to run a tor middle-relay if you are behind NAT and cannot control the firewall.
Has that changed or are there other ways I can help the tor network if I have a server with 1 Gbps bandwidth which sits behind a firewall I cannot change?
There is a possibility that the snowflake project might be of use to you. While the frontpage talks mostly about browsers, there is an experimental Go-based standalone implementation which might be able to run on your behind-the-NAT server. It isn't a proper Tor relay, merely a way for those who are severely restricted to get into the Tor network proper, but if you truly cannot configure any port on the firewall (remember the ORport doesn't have to be a common port like 443) to be forwarded to the internal server, I believe that being a Snowflake node is the only option left available.
