I just realized that if the router has its own remotely-accessible backdoor, then intelligence agencies and hackers can remotely connect to my router and then connect to CPU backdoors behind the router.
Even if CPU backdoors don't know how to connect to the internet on their own via the router's internal VPN, intelligence agencies can connect to the CPU backdoors via the backdoors on the router.
Thus, it's best to buy only old CPUs and old motherboards that you can flash coreboot or libreboot onto.
I'm going to keep using and buying old CPUs until open-source CPUs appear.
If the router itself doesn't have a hardware backdoor and has coreboot or libreboot and allows internet connection only through its internal VPN, then you can use any computer behind the router safely.
Even if CPU backdoors don't know how to connect to the internet on their own via the router's internal VPN, intelligence agencies can connect to the CPU backdoors via the backdoors on the router.
Thus, it's best to buy only old CPUs and old motherboards that you can flash coreboot or libreboot onto.
I'm going to keep using and buying old CPUs until open-source CPUs appear.
If the router itself doesn't have a hardware backdoor and has coreboot or libreboot and allows internet connection only through its internal VPN, then you can use any computer behind the router safely.