Seeing it on your PC
A game, the Xbox app or Game Bar using 3074 during online play.
Should you block it?
Normal for games. If the Xbox app reports a strict NAT type, the fix is usually on the router (UPnP or a port forward), not in Windows.
Check it on your PC
Run this in PowerShell to see what is using port 3074 right now, and which program owns it:
Get-NetTCPConnection -LocalPort 3074 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}Get-NetUDPEndpoint -LocalPort 3074 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}No output means nothing is using the port at the moment. For every connection at once, paste netstat -ano into the netstat explainer.