Recommended and mentioned products
OPNsense® you next open source firewall. Free Download. High-end Security Made Easy™. Offers Intrusion Prevention, Captive Portal, Traffic Shaping and more.
VyOS in an open source Linux-based operating system sold and distributed by Sentrium corporations. It is geared toward IT specialists and network administrators for the purpose of securing network and company data... read more.
Try VyOS. It's based on Vyatta, which is also what Ubiquiti's EdgeOS is based on. It's all CLI-only, but it's pretty powerful. https://vyos.io/.