Hello there.
By your linked post, it sounds like you want to use that older PC as a router. I have heard a lot about
Endian Firewall. My uncle uses it, and he said it is quite powerful. It is a Linux distribution made to be a router/firewall. The only thing, though, is that I am not sure the older system meets the hardware requirements. It's something worth checking into, though.
HOpe this helps.
Take care.
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