The MacBook 2,1 is almost unique in being supported by Coreboot and Libreboot. Furthermore, because it had an Atheros wireless card, you didn't need any blobs at all. Only two old Thinkpads are comparable, among x86_64 machines.
The MacBook Air 11 Late 2012, which was used as a daily runner by Linus for a number of years, was a pure Intel machine. Except for a weak Broadcom card, it was flawless with a stock kernel. Plus, it was silent, small and fast. The only comparable machine in terms of silent operation, cost and Linux support was IMHO the Xiaomi Notebook 12.5, which was released quite recently.
The problem with ARM Macs is not just secure boot. The secure enclave chip already gave serious trouble when trying to run Linux on their last Intel machines, as e.g. the keyboard doesn't show up as a standard USB device. So I don't have high hopes.