My 2015 Mazda 3 is rootable. Then Mazda made them unrootable with an update, and then the leet hackers started physically opening them up and rooting them with UART.
Hondas infotainment is just android. And at least on my friends 2017 Civic you could get to the regular ass android interface. Most of them are some flavor of Linux.
Also you can install whatever head unit you want on most cars. You can even buy a head unit from china that will match your cars trim for like $300 from china.