Which cryptographically secure pseudorandom number generator does Debian kernel use? On FreeBSD and recent releases of macOS, Fortuna) is used. What about Debian?

According to Wikipedia, ChaCha20:

> In October 2016, with the release of Linux kernel version 4.8, the kernel's /dev/urandom was switched over to a ChaCha20-based cryptographic pseudorandom number generator (CPRNG) implementation[16] by Theodore Ts'o, based on Bernstein's well-regarded stream cipher ChaCha20.

This is also discussed on the Cryptographically-secure pseudorandom number generator page at Wikipedia.