The British spelling was used by Philips when they launched the Compact Disc with Sony.

Disk was used by American companies inventing hard disks, floppy disks etc.

British software often used "disc" for both, e.g. RISC OS on Acorn/ARM/Raspberry Pi [1].

[1] https://arcwiki.org.uk/index.php/RISC_OS_3 (see screenshot)