Is TLS 1.3 supported in Blazemeter?
TLS 1.3 requires at least Java 11, so java version of your test should be set to Java 11 and the JMeter version to 5.3:
Also user.properties should be modified to read https.default.protocol=TLSv1.3
And that file should be uploaded to the test scenario as well.
However, there is a bug as described in https://issues.apache.org/jira/browse/HTTPCLIENT-1967
It is taken care of in Java 12 which is not yet supported in Blazemeter.