Port 8333 closed, fwd on Router OK, firewall port open, full-node not reachable I have set up my bitcoin/lnd full node and found out that port 8333 is closed.

When checking using https://bitnodes.io it tells me it's down

I've checked the router config and port 8333 is forwarded to the IP of the node.

If I scan or use telnet to connect locally to my node, it seems to be blocked.

Also ufw has been checked and sudo ufw allow 8333/tcp has been added.

As well sudo netstat -tunlp tells me that the port is in listen state.

Now, I'm kind of stuck and looking for help.

Many thanks in advance for a reply and stay healthy.
First, check your router opens that port too and redirects that port to you computer.

Then check CGNAT. If the external IP address your router shows isn't the same as you find when you search for "what is my ip", your ISP is giving the same IP to multiple customers. So you won't be able to open a port.