Maybe a case for the EU? I mean, they like creating laws limiting the power of big tech. Maybe there should be a law that requires all services that are used by public institutions and commercial transaction providers to be transparent to the public and therefore open source. And as a platform provider, they should be required to offer APIs to let users install alternative implementations.
Might require some fine-tuning, but you get the idea.
You can only run LineageOS on smartphones that allow unlocking the bootloader (which is more and more rare), and properly release the kernel source-code (many still don't, especially low-end MTK-based phones...)
Also, how’s isolation on LineageOS for mobile apps? I think I’m getting to the point where I’m thinking of ditching Apple again