Build a firewall & router with OPNsense

Lots of online recommendations for this firewall:
https://www.pcworld.com/article/2548020/build-your-own-router-and-firewall-with-opnsense.html

NOTE: this can be run on a dedicated mini-PC or as a virtual machine ...

OPNsense is an open source, FreeBSD-based firewall and routing software developed by Deciso, a company in the Netherlands that makes hardware and sells support packages for OPNsense. 
https://en.wikipedia.org/wiki/OPNsense

https://opnsense.org/

https://www.deciso.com/opnsense-25-7-visionary-viper-launches-with-smarter-security-and-faster-setup/

https://opnsense.org/get-started/

The recommended specifications to run all OPNsense® standard features ensure that every feature is functional and suitable for most use cases.

Type                                     Description
Processor                             1.5 GHz multi core cpu
RAM                                     ≥ 4 GB
Install method                       Serial console or video (vga)
Install target                          120 GB SSD

Firewall:   Stateful firewall with support for IPv4 and IPv6 and live view on blocked or passed traffic.

VPN:  Integrated support for IPsec (including route based), OpenVPN as well as pluggable support for Tinc (full mesh VPN) and WireGuard.