TLDR: Microsoft worked with Intel and AMD to develop Pluton which is basically a TPM chip designed to prevent running non-microsoft approved software. It will likely make it impossible to boot un-approved linux distros, bsd, and likely will make it very hard to run any un-approved software in the future.
This CPU "feature" is very likely to be a requirement for Windows 12 in 2024. Meaning nearly every computer available will have this and the majority of manufactures will not allow you to unlock the bootloader.
Similar situation to running LineageOS or PostmarketOS phones. For now, it can be "disabled" in bios on most of these computers, but that's simply a choice the OEM is making and will no longer need to make once this has become prevalent without any real pushback.
My understanding is that, funny enough, Google Pixels will probably always allow you to unlock the boot loader. Something about how Android developers need a phone they can do that on to properly develop apps, but idk I'm not a nerd.
In general the high end "flagship" devices have unlockable bootloaders, but the devices that the vast majority of people can afford do not. I expect to see a similar thing in laptops. If you can throw down 2-3,000 USD on a new XPS or Thinkpad X1C you'll likely get the privilege of an unlockable bootloader. For most of the non-US world that's a huge chunk of everyone (including developers) salaries.
When people discuss Framework laptops or whatever, this is what comes to mind. They're priced at a pretty inaccessible price point already and people tell me that Framework laptops being reliably sold at that price point is a success for upgradeability and right to fix laws because it shows there's demand for it, but it really isn't. What succeeded here was Framework establishing a "tinkerer" niche, one that grants you upgradeability and freedom to install whatever software you see fit without jumping through weird hoops at a premium. Cisco did this with WRT54G and WRT54G-L routers, the second had a steep price difference even though the hardware was essentially the same, just because it allowed you to flash in OpenWRT without using exploits. It's the same for enthusiast phones, most if not all of them allow you to flash in your own bootloader without exploiting, but most enthusiast phones are sold at flagship prices. It's just capitalism that's so incredibly good at spotting its own rot and commoditizing the solution.