For desktops/laptops your best bet is

Libreboot – Free and Open Source BIOS/UEFI boot firmware

Libreboot – Free and Open Source BIOS/UEFI boot firmware

Libreboot – Free and Open Source BIOS/UEFI boot firmware

the fastest one you can get is an i5 Thinkpad T480. Ideally flashed by yourself and all that.

system76

for modern computers. Coreboot firmware with ME_cleaner, but with weaker ME disabling guarantees than libreboot. I wouldn't put my most sensitive stuff on these, but a great use case for something like QubesOS where you need lots of threads to maintain performance. Phones are mostly a lost cause until we can get free and open source firmware SoCs. GrapheneOS has great privacy guarantees on a software side, but the Titan chip is a major black box, same with the modem and the SoC as a whole.