Ubiquiti EdgeOS based edgerouters are what I prefer as a greybeard sysadmin type who has dealt with everything under the sun. It's VyOS (Vyatta) based, they are now complying with gpl afaik, and their hardware is really good for the price/performance ratio. The edgerouter-x or lite can be found for ~$99 and is a great piece of gear.
Another option would be your own hardware with pfsense (bsd) or ipfire(linux).
Even further would be your own hardware with linux and write your own nftables or bpf.
Another option would be your own hardware with pfsense (bsd) or ipfire(linux).
Even further would be your own hardware with linux and write your own nftables or bpf.