I'm using latest virtualmin with Let's encrypt certificates. Although everything works well on most devices the certificate Chain has issues:
Chain issues: Incorrect order, Extra certs which lead to site unavailability on some android devices due to err_cert_authority_invalid error.
BTW virtualmin.com has correct certificate chain https://www.ssllabs.com/ssltest/analyze.html?d=virtualmin.com&hideResult...
and as you can see there's only one
Let's Encrypt Authority X3 in your setup, but in my setup which was automatically configured by virtualmin there are Let's Encrypt Authority X3 and
Let's Encrypt Authority X1 , I beleive the
Let's Encrypt Authority X1 certificate is not required but is concatenated with X3 certificate into letsencrypt-lib.pl into one cert file.