Pihole+Unbound prevents one single device from accessing the internet

[deHakkelaar]

What do you need the logs for?

Client query logging can be looked up in the Pi-hole logs and long term database.
If its for diagnosing, you only have to up verbosity to the level that you desire and loopup the logs with journalctl:

Unbound doesn't work, connection timed out

Is this all there is when things go south? (EDIT: with verbosity set to 3?) If so, increase verbosity to get more details? pi@ph5b:~ $ man unbound.conf [..] verbosity: <number> The verbosity number, level 0 means no verbosity, only er‐ rors. Level 1 gives operational information. Level 2 gives detailed operational information. Level 3 gives query level information, output per query. Level 4 gives algorithm …