Debian buster VM on an old CPU without RDRAND takes about 5 minutes for the kernel crng init to complete and for sshd to start accepting connections. Stracing the sshd process shows that it's indeed blocked on `getrandom()`.

In some ways, it's very much WONTFIX because something like sshd might actually need the entropy. I'm glad that systemd has proper workarounds implemented so that the machine actually boots out of the box, though.