I’m more thinking of patents and licensed third-party technology and firmware. There are standard tech stacks controlled by industry associations that you simply can’t open source because the association would sue you and kick you out.

These associations do not just exist in vacuum. They have licenses like this because law allow it and it's beneficial to them. Once there are regulation that demand something else they'll just follow the law.

Also it's not like every single bit of firmware / software must be open sourced - it's could very much be trade off where devices just need to be unlocked for modification and documentation made available.