I am getting the same result on the SSLlabs server test. It seems to me that there is a bug on their end, as ISRG Root X1 has nothing to do with identrust.com...
The DST Root CA X3 certificate (from IdenTrust), which has cross-signed the ISRG Root X1 certificate that Let's Encrypt uses, has expired, but is still part of the "default" chain for compatibility with old Android version. But as it's expired, IdenTrust is no longer publishing the CRL for it. But this shouldn't matter, unless somewhere there's a client that is trying to check the CRL of an expired certificate. I find it unlikely that the missing CRL would be causing any actual problems, unless you're actually seeing a client giving some message saying so. SSLLabs is just correctly reporting that the root is expired, and has a missing CRL, but that should be irrelevant to most actual use cases.
Regardless of the status of this path, if "Path #1" is valid and that chain is being provided, then clients should be connected via "Path #1" without issue.