Ran into todays problems with the expired root certificate on my website www.rejsa.nu. Trying to delete and renew my certificate this also failed due to this:
root@no:~ # curl https://acme-v02.api.letsencrypt.org/directory
curl: (60) SSL certificate verify result: certificate has expired (10)
More details here: https://curl.se/docs/sslcerts.html
curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
Sorry I don't know the specifics for that but you need to get it to add the self-signed ISRG Root X1, which you can download in various formats from here: Chain of Trust - Let's Encrypt
If you have a /etc/ssl/ it may be something under there you need to update (in a subfolder), someone else with more familiarity with FreeBSD may be able to help.