TLDR: UniFi Network Application 7.4.162 may start blocking Tor, even though the corresponding option is disabled.
I just spent a couple hours troubleshooting my Bitcoin Lightning node because suddenly (over night) all channels where down. After a while I realized that, while the Bitcoin node was still connected, it only connected over clearnet and no longer Tor. Hence – starting to troubleshoot Tor. Nothing really conclusive in the log files, but eventually I tried connecting to Tor from another device in the same network – also doesn’t work!
So I suspect it could be UniFi blocking Tor. But the relevant configuration still has the Dark Web Blocker disabled, therefore should not block Tor.
In my despair I came across Reddit, and of course it helps: Unifi blocking Tor traffic even though it’s asked not to. So I enable the Dark Web Blocker option, save, and disable it again – Lightning channels are up again, problem solved.
Root cause analysis: my UniFi firewall auto-updated to this version at night, and the same minute my channels go down. I know this courtesy of the Lightning Watch Bot, much recommended!