I have no deep knowledge of this, but i guess there is a difference between sponsoring and owning. A lot of big FOSS projects have indeed corporate donations, but i think for the most part corporate cannot force them to do things (the only exception i know of being the deal between Mozilla and Google). Of course, they can threaten to cut fundings, but i think it isnt a real problem (for now) for various reasons : linux ecosystem is still niche enough to be uninteresting for big corpos, donations help projects get better quicker but you can always fork them and come back to more humble progression if needed (not 100% sure, im not very tech literate, but that’s a feeling i get), and i guess FOSS ecosystem also provides big corpos with talented people and occasionally interesting pieces of software, so they have a bit of interest in keeping it alive.
If you want to go towards the least corporate options, you can try the most niche linux options. Linux Mint is based on Ubuntu, made by the enterprise Canonical, which has a somewhat bad reputation in the linux corporation, for being a bit too centralized i guess ? I use it as it is perfect for a not skilled user like me, but if you want to be independant of tech companies, maybe that’s not the perfect choice.