There were a case back in the days of PS3, where sony removed ability to run linux from new versions of console. They were sued and lost, but still decided to pay the fine, rather than returning functionality.

The main issue as I see it, is that they sell consoles as cheap as possible (previously they even sold them at a loss) and then return such investment by selling you games and subscription. By opening ability to install linux, not only they will loss profit from upper mentioned part on existing devices, but there a chance people will start buying PS5 to use as a regular desktop or general server or whatever, due to being simply cheapest prebuild option available for such specs. Same point was rised by Valve actually, they too was afraid that if they start selling gabebox at loss, people will buy them for anything, but playing games.