The collection method is international conventions, seminars, and exhibits. The wording about offers or invitations for cultural exchanges, individual-to-individual exchanges, and ambassador programs matches that category.

Why this fits

That phrase is used as an indicator of this collection method in counterintelligence training materials. It also appears in multiple question- and-answer sources with the same answer.

Quick note

One source mentions elicitation as a related concept, but the best match for your question is still international conventions, seminars, and exhibits.

TL;DR: International conventions, seminars, and exhibits.