Second question: is the log pipeline available for Kolide K2 users? (see e.g. https://www.kolide.com/docs/using-kolide/log-pipeline/configuring-splunk-hec)

Yes, the log pipeline is available for K2 customers. Do you see it under the "Tools" dropdown?

Hmm - I do not! (and I am an admin)

I can take a look! Would you mind DMing or sharing here the name of your company?