I can't tell if you offering this as something that's sane to do or not. I think you should absolutely be able to install the software you want in your lexus; the built-in software is often terrible (yes, including tesla).

> You can't install anything unapproved by Lexus on a Lexus system

Only as of recently and still rarely. Most cars of the world hardly used original parts for repairs. The whole auto repair industry is based on a bunch of hacks and fixes that are not licensed by holy overlords. Most of car computer AFAIK can be sideloaded and hacked with exception of something like the infamous john deere.

Speaking of which, John Deere has been in the news for this for ages now and maybe it's time to seriously liberate car software as well.

The difference depends on if you are talking about what is legal (eg right to repair) or what is possible by the consumer without modification. Legally you can do whatever you want since you own the hardware - but in both Apple’s case and Lexus’ case, installing a non-OEM part will void the warranty on that part, or in Apple’s case, the entire kernel since you’re modifying that kernel (although it’s easy to factory reset an iOS device and remove the modification without a trace).