The big tech is, indeed, trying to extend their reach to linux and open source in general, but it's still the best we have, and it still goes against them. The good thing about open source is that it's resilient and highly adaptable. A few distros have been making experiments with other kernels, and if things go too bad, they might replace linux with anther one and we will persevere. It's also possible for some group to fork linux and create a parallel community version, like happens with a lot of open source software developed by big tech companies. But you don't need to worry, because linux remains fine and will probably be for a good while.