Electronics before Linux
Before embedded microcontroller systems there were application specific ICs like SANYO LM8560 (alarm clock ic)  and lumped logic like that used in the ROLAND CR-78 (drum machine)
Once microcontrollers became economial they were embedded with a first a non-hosted application (the microcotntroller boots straight into the application code)
Example pc keyboards and keyboard interface ics.
And later (once there was suffuicient complexitity) with operating syustems hosting the applications software.