I'd encourage you to do your own research on this. The kind of research where you assume you're getting a soon-to-be-abanonded piece of techno-capital-consumerist ewaste, and critically evaluate anecdata against a rubrik composed from spending time researching the hairy corners of the space. This comes from a bleeding heart optimistic burned almost too many times.

Here are some items to look for: - a device tree for the chipset for your device - a u-boot fork or patches for the chipset/device/both - a Chromebook built with that chipset, due to how ChromeOS development is done - any sign of commitment from the chipset manufacturer

This topic is a lot like early Android bootloaders before... one of the early Motorola devices. Before there was a set of expectations/framework-support/etc for unlocking. That first unlockable Motorola device, there was 9 months of every wise-guy on the Internet swearing it was just a matter of time. And often it is, but only due to what amounts to luck.

Hint: there's a reason that every single Linux enthusiast isn't running a ARM laptop. There's a reason that Linux folks are excited about the Linux on M1 project even though it means jumping through hoops and reverse engineering and playing ball with Apple.