I'm usually in this community support area quite a bit, but for some reason, I'm just now seeing this issue, 5 months after the fact. While I don't want to revive an old thread, I believe I have some input, to help resolve this issue.
I've been in contact with Jetpack about a different issue, but a similar error in their debug info. I'm actually getting ready to post a new support issue, in the EE community about it. I believe the issue you are having within the Jetpack debug info is related to how your "WordPress Address (URL)" and "Site Address (URL)" are defined in the General Settings - at least that was my issue.
In order for many of Jetpack's features to work correctly, with an EE/Let's Encrypt installation, both of these addresses must start with "https://"
In support of my suggestion above, I've provided an email response from Lisa (one of Jetpack's happiness engineers), about my "similar issue", as it relates to XML-RPC requests:
Can you confirm these settings, in your WordPress' General Settings?