Portmaster is described as 'All-Around System Privacy' and is an app in the Network & Admin category. There are eight alternatives to Portmaster for a variety of platforms, including Windows, Linux, Android, Raspberry Pi and Mac. The best alternative is AdGuard, which is both free and Open Source. Other great apps like Portmaster are simplewall (Free, Open Source), Pi-hole (Free, Open Source), GlassWire (Freemium) and Little Snitch (Paid).
NetLimiter is an ultimate Internet traffic control and monitoring tool designed for Windows. You can use NetLimiter to set download/upload transfer rate limits for applications or even single connection and monitor their Internet traffic.
Gufw is an easy, intuitive way to manage your Linux firewall. It supports common tasks such as allowing or blocking pre-configured, common p2p, or individual ports port(s), and many others! Gufw is powered by Uncomplicated Firewall (ufw).