I'm trying to figure out how to configure my UFW, and I'm just not sure where to start. What can I do to see the intetnet traffic from individual apps so I can know what I might want to block? This is just my personal computer and I'm a total newbie to configuring firewalls so I'm just not sure how to go about it. Most online guides seem to assume one already knows what they want to block but I don't even know how/where to monitor local traffic to figure out what I can/should consider blocking.
I would advise that you ignore a lot if the advise here and do your own research. You probably don't need a local Firewall and if you want to block content use DNS and browser extensions
If the computer never leaves the house, maybe. If it's ever on public Wi-Fi though, default deny inbound at a bare minimum. Linux computers with cups installed and running but no firewall were revealed yesterday to be vulnerable to RCE.