With UCS 4.4-8 errata 1057 an below access of Let’s Encrypt signed sites is not possible since 2021-10-01 as the certificate is not trusted.
You can test it by using tool like
root@dc1:~# curl https://dc1.fqdn-host.de curl: (60) SSL certificate problem: certificate has expired
In some cases you need to remove the old R3-certificate and refresh ca certs:
rm /usr/local/share/ca-certificates/lets-encrypt-r3.crt update-ca-certificates --fresh