Step 1
How did I replace SysVinit with Systemd in Debian 10?
Snap can not be installed without Systemd.
Step 2
How do I install Snap to Debian 10?
Step 3
apt-get remove certbot
certbot.eff.org/instructions?ws=other&os=debianbuster
Step 4
snap install --classic certbot
certbot.eff.org/instructions?ws=other&os=debianbuster
Step 5
ln -s /snap/bin/certbot /usr/bin/certbot