Proof of recognition beyond applicants occupation

Hi everyone
How do I prove this with webinars. I have hosted a couple of webinars teaching participants on AI, data analysis and SQL. How do I present this evidence

Is this Webinar noted (archived/recorded) somewhere on the open internet? If so, provide a screenshot and a link to that. Even if you have it on a private site/intranet, you should still be able to screenshot and explain that it is behind authentication.

If neither of the above is true, perhaps the organisers of the webinar wrote something to you in emails, specially after the webinar was completed - perhaps thanking you or such. You could provide such emails too, though its effectiveness wouldn’t be as good as the above 2 options.