I get you in principle, but the company should still be allowed to sell hardware with some default software installed, because if I had to search for someone on the internet that wrote software for my specific smart TV, washing machine or whatever this becomes much more painful.

I would rather see a 'right to repair' extended to software bundled. Any device or software that can connect to a network or can be interfaced with in any way is prone to security (or any other) bugs, which the customer should have the right to fix themselves, because they bought it, and in order to do so, the company needs to hand out the source code and documentation for all their devices.

Also about vendor writing Linux drivers, you probably don't want them too, there are already vendor board support packages (BSP) out there that enabled their hardware on Linux, but those are overwhelmingly abysmal in quality.

What you rather want is for vendors to upstream their driver into the kernel, so that it is properly integrated, doesn't break the hardware of others and has a high quality, but that process is not something you can regulate and force.