Otto's workaround also resolved the issue for me, thanks Otto! I do not know what caused the issue as I did not upgrade, but some details below just in case it is helpful for anybody:
I'm on Debian 10. Did not upgrade. Last I remember before issue was adding some cryptographic libraries with pip/conda and following instructions here [0] to add to apt sources to upgrade system Python. Found out because could not SSH into GCP instance next day after restart. sshd was failing on start finding libcrypto. Tried adding apt commands to startup script for VM and using chpasswd to add temporary password for access through the serial console, but both of those commands similarly failed without libcrypto. Adding Otto's fixes to the VM's startup script got SSH working again. [0] - https://www.linode.com/docs/guides/how-to-install-python-on-debian-10/#how-to-upgrade-from-python-37-to-39
