It always depends on what you want to do, if you have to look at the forum an old PC with a chip before 2007 and Linux do their job perfectly, then on the internet side you just use TOR -> VPN and you're fine
Yes, this forum doesn't require much CPU power + ram and any system that's created before 2007 can be used to browse the forum without any issues and any chip will do the job perfectly when Linux is installed in it.
I used to use a very low-end laptop from 2006 and on that laptop I installed Lubuntu, and to be honest the forum's experience on that laptop was fully okay. I didn't face any lag at all.
I don't remember fully but I'm pretty sure that in 2017 or 2018 I even used this forum on my Raspberry Pi 3B and even on that system the forum worked without any issues.
As a trader I needed to sift to a powerful system that's the reason why I moved to new generation laptop but I would still say that if someone's intention is to use this forum then even a weak system that can browse the internet may work like charm.
I've not tried it myself but I'm pretty sure that even a system with 256 MB ram and 1 GHz processor can easily handle this forum if Puppy Linux or another low end Linux distribution is installed in that system.