raspberry pi – Update “let’s encrypt” certificate from command line

yeah, certbot renew is the way to go. Do it without --force-anything. If the certificate isn’t due for a renewal, it isn’t due.

Don’t know what Linux distro “NextcloudPi” (never heard of that) is based on. Chances are, the certbot package came with a timer that you just have to activate to do these renewals automatically. Check whether systemctl enable --now certbot.timer reports success; if it did, congratulations, your certbot installation came with a timer for auto-renewal that you just had to activate!

If your certbot did not come with a timer, this answer describes how to add your own and activate it, so that your certifcates never expire.