You're the idiot talking straight out of your nether regions.
ALL of those systems allowed for full control of the hardware and for you to boot any OS of your choosing. You are trying to conflate the ownership of the BIOS code with a regime that prevents the end user from running any OS you like.
There have always been alternate operating systems. The field for PC based operating systems used to be actually rather competitive. There have also been complete or partial replacements for the system software in systems like the Amiga or Atari ST.
The first Linux user I ever encountered ran it on a Falcon.
You're either stupid or a shameless liar.