Hello,

After reconfiguring on the 'core-updates' branch, systems using the
OpenSSH service will occasionally (not always!) hang forever during
boot, waiting for entropy.  Moving the mouse or mashing the keyboard
allows the boot to proceed.

I don't think this is limited to OpenSSH, but anything that calls
getrandom() during startup.

There is some information about this problem and various workarounds
here, including links to recent LKML discussions:

https://daniel-lange.com/archives/152-hello-buster.html

For Guix, I believe adding (service urandom-seed-service-type) to
%base-services should be sufficient, but have not verified this yet.