Best posts made by Geosearchef

Forwarding ports is unnecessary.
The error you posted is normal.

The main issue is this:

java.util.concurrent.CancellationException: null
	at java.base/java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2468)
	at com.faforever.iceadapter.ice.PeerIceModule.lambda$gatherCandidates$4(PeerIceModule.java:118)
	at com.faforever.iceadapter.util.Executor.lambda$executeDelayed$0(Executor.java:16)
	at java.base/java.lang.Thread.run(Thread.java:832)
Nov 30, 2020 8:17:08 PM com.nbarraille.jjsonrpc.JJsonPeer sendNotification
INFO: Sending Notification:{"method":"onIceConnectionStateChanged","params":[82574,47273,"disconnected"],"jsonrpc":"2.0"}
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: ICE state changed from Waiting to Terminated. Local ufrag 357851eod9cggh
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: socket closed
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Closing.
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: Socket closed
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: Socket closed
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: Socket closed
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: Socket closed
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: Socket closed
Nov 30, 2020 8:17:08 PM org.ice4j.util.Logger log
INFO: Failed to receive: java.net.SocketException: Socket closed

This means your operating system or antivirus is closing the socket and not telling the adapter why.
This only occurs on less than a few percent of devices. I spent a lot of time debugging that and sadly didn't find a solution, the issue lies somewhere within proprietary code of your operating system manufacturer.

Try the options suggested in https://wiki.faforever.com/index.php?title=Connection_issues_and_solutions#Unable_to_connect_to_someone
in the order they're listed in. Each is more likely to fix the issue, e.g. VPN worked on one of my machines when I had that issue.