I'm a huge fan of OpenWrt. When I got 10 Gbit internet at home I had to replace my old Ubiquiti USG3 on the cheap so I built a router out of a $80 Lenovo ThinkCentre Tiny.

I tried OPNsense and pfSense on advice but they could never crack around 5 Gbps throughput even with a bunch of tweaking, but OpenWrt gave me the full 10 gbps out of the box with no hassles.

I also replaced the Ubiquiti firmware on an EdgeRouter with OpenWrt and it boosted the throughput from around 1.3 Gbps to 1.7 Gbps.

The OpenWrt UI for configuring the firewall is probably one of my favorite firewall UIs of all time. Before OpenWrt I could never wrap my head around those "local" etc ruleset names in more traditional routers, I had to look them up again every time I edited the config. Just being able to say "I have these networks, let this one do this to that one" is very easy to understand.