Why are Linux operating system providers taking it upon themselves to comply with the California law especially if they are not selling anything. Since it is just a downloadable piece of software then it is up to California state to set up a firewall to protect themselves from such harmful software.

Let's say I am a generic linux developer who develops variants of Debian Linux while sitting in my basement in any part of the world.

If one country wants to ban my software because I don't ask for their age, then set up suitable protections for your citizens.

Don't force me to do that. I am not responsible for protecting your citizens.

That is like saying if Saudi wants your id to make sure only males can download operating systems, so now will I add another restriction.

At least China takes it upon themselves to ban sites that they deem harmful for their citizens rather than forcing devs.