Installing Linux bare onto a Chromebook involves unplugging the internal battery (or buying a cheap special USB thing) to disable the hardware write protection and flashing a custom BIOS. Some models have issues with basic things like sound output not working through speakers or headphones or both. From experience I don’t recommend.
If you still really want to though there are two websites that are really useful and should have up to date information.
Chromebooks are locked down yes, but they do give you the keys. It involves unplugging the internal battery to be able to modify the hardware write protection, entering dev mode to disable the write protection, and then flashing a Coreboot port onto the firmware. Even then, a lot of basic things may or may not work once you’re booted into Linux. From experience I don’t recommend.