I don't understand the complaint.
My Pi4 shows:
uname -a
Linux raspberrypi 5.4.79-v7l+ #1373 SMP Mon Nov 23 13:27:40 GMT 2020 armv7l GNU/Linux
And it can:
sudo apt install snapd
sudo snap install core
sudo snap refresh core
sudo snap install certbot --classic
/snap/bin/certbot --version
returns:
certbot 1.10.1
NOTE: If you have installed snap [apt install snap], you will have to install+refresh the snap core.
[don't install snap - install snapd]