Route pc's traffic through gateway hosted on another computer

Hello! Hope you’re doing well. Essentially, so did I, but it was not long before i’ve destroyed my evening trying to solve this, to say mildly, a bit strange task.To begin with, I want to assure those who had already thought of replying to this post with the warning - yes, I do acknowledge all the risk i’m going to introduce into my life, and i am 100% sure that it’s what i want to achieve.

So, these are inputs:

  1. An old PC i need to connect to the internet as secure as I can. I’ve already tried Tails and that definitely wouldn’t work here.
  2. Right next to it i have my beautiful test setup(linux host + several vm’s, including ready-to-use gateway).

What i did was: installed whonix-approved preconfigured debian distributive on PC #1, connected it to an available ethernet port on the PC #2, checked that configs /etc/network/interfaces and resolv.conf were suitable(aka had standart static ip settings that would help it find gateway) and tested two situations.

One, where i didn’t touch host settings at all, connected ethernet adapter straight to gateway(in QEMU-KVM, thats what i use), and, unsurprisingly, result wasn’t wery marvelous - in the end i needed all VM’s to be in a single internal network.

And second, where i tried my best to setup bridge connecting ethernet adapter and the exact network i needed - internal one - and, as you’ve probably already guessed, at least by me mentioning network’s title one more time, this had also failed.

My question is: what you think would be the most practical way to solve this puzzle, as i would really appreciate using this kind of setup in nearest future. Thank you for time that you’ve spent reading all this, and i would be glad to give any logs/configs that can help you understand my problem.

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