Just use certbot. It automatically sets up a scheduled task to renew your SSL/TLS certificates in the background, typically using a systemd timer that runs twice a day. I do not know why people using LetsEncrypt would not set up certbot along with it, that is how I do it. Some nginx config + certbot.
Maybe the situation's improved, but I found certbot from system package managers would diverge from latest version, sometimes significantly, like support for DNS challenge APIs breaking. I switched to ‘acme.sh’ for most machines and haven't looked back. It no longer has Let's Encrypt as its default issuer, but you can set it back to LE with one config command.
