What are some alternatives?
When comparing Filseclab Personal Firewall and NetGuard, you can also consider the following products
TinyWall - Lightweight and non-intrusive firewall
LuLu by Objective-See - LuLu is the free open-source macOS firewall that aims to block unauthorized (outgoing) network...
Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
Windows 10 Firewall Control - Windows 10 Firewall Control: simple and exhaustive solution for applications network activity controlling and monitoring.
Mobiwol - Mobiwol is a NoRoot Firewall
OpenSnitch - OpenSnitch is a GNU/Linux port of the Little Snitch application firewall.