If you've made a pull request to Mbed TLS, you've noticed that some of the continuous integration happens on a private server run by Arm.
For jobs that ran since yesterday, if there are failures, you can now see the name of the failed tasks next to “PR-NNN-head TLS Testing” or “PR-NNN-merge TLS Testing”. See https://developer.trustedfirmware.org/w/mbed-tls/testing/ci/#identifying-jen... for more details.
If this isn't enough, an Arm employee can copy the logs from the server. Please ask in a comment. We hope to post logs automatically (https://github.com/ARMmbed/mbedtls/issues/3633) but I can't give a due date for that.
We are planning to move to a public server run by TrustedFirmware, but this can't happen until some time in 2021. Please bear with us in the meantime, and thank you for your contributions.