Certificate expired for root domain but not www subdomain

[ahelwer]

The cert of the root https://idris-lang.org domain is expired:

> curl -v --head https://idris-lang.org
* Host idris-lang.org:443 was resolved.
* IPv6: 2a00:1098:0:86:1000::11
* IPv4: 185.199.108.153, 185.199.109.153, 185.199.111.153, 185.199.110.153
*   Trying [2a00:1098:0:86:1000::11]:443...
* Connected to idris-lang.org (2a00:1098:0:86:1000::11) port 443
* ALPN: curl offers h2,http/1.1
* (304) (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/cert.pem
*  CApath: none
* (304) (IN), TLS handshake, Server hello (2):
* (304) (IN), TLS handshake, Unknown (8):
* (304) (IN), TLS handshake, Certificate (11):
* SSL certificate problem: certificate has expired
* Closing connection
curl: (60) SSL certificate problem: certificate has expired
More details here: https://curl.se/docs/sslcerts.html

The www subdomain is still fine and shows a valid cert from letsencrypt.

We ran into a similar issue in the TLA+ community, see tlaplus/tlaplus#1141.