Are there different implementations of Coreboot?
Coreboot is kinda like the Linux kernel. It’s a low level codebase that handles the super early initialization (from cold power-on) of the various bits of silicon in your computer. It’s the software that is initializing your DDR memory controllers, pulling the CPU up from 16bit real mode thru to 64 bit, etc.
I think the Linux kernel analogy is especially apt when you think about something like a BIOS configuration screen. You wouldn’t expect the Linux kernel to present a GUI on a screen. It provides the low level DRI stuff. But then you need something like Mesa to implement 2D/3D rasterization APIs, a Wayland display server implementation (e.g Weston), and then finally a window manager (like Mutter) to handle drawing pretty UI elements and such.
So yeah, coreboot isn’t really for someone who just wants to press F1 and configure some settings graphically before booting into Windows or a vanilla Ubuntu installation. It’s for power users, system integrators, and such. Of course, there’s nothing stopping someone from implementing a fancy GUI payload on top of coreboot that functions similar to what you typically expect from a proprietary BIOS blob.
To this day, no idea how to switch to legacy mode
Someone with more experience can speak specifically to this, but if you’re referring to CSM mode I dunno if coreboot would ever bother supporting that.
As mentioned, Coreboot is very low level. It configures memory controllers, uploads FSP blob to your Intel CPU, and then it hands over to a “payload”. The typical payloads you’d be using are either SeaBIOS (for the legacy BIOS you’re probably looking for) or TianoCore (for a UEFI boot environment).
Coreboot is very niche. As noted in this thread, you can count the number of standard mainstream ATX/ITX mainboards produced in the last decade supported by coreboot on one hand. It has a lot more adoption in the netbook world because Google chose it for Chromebooks. But Google doesn’t want you to configure a Chromebook any further than the cart customization you do every 3 months in their checkout page so that we can all drown in e-waste.
I can imagine that coreboot gains a lot more traction over the next few years, which attracts more vendor interest and demand for end-user-friendly GUI configuration tools, either at F1 on boot, or from userland in a booted OS.
In summary, I wouldn’t expect Framework to completely drop the current InsydeH2O payload shipping on their laptops today. In fact, I would expect a consumer-focused company like Framework to continue shipping that BIOS (or something like it) by default indefinitely.
As I’ve noted earlier, it’s more about what happens 5 years from now when Framework stop supporting their old 11th gen laptops. It’s also about enabling folks to do whatever they want to do with their Framework mainboards once a laptop has reached its end of life. Or put differently, preventing an item from ending up as e-waste.