For two of our clients, simple outreach through emails(lemlist) has worked really well.
You need warm the email id, I trust lemwarm.
Increase the daily send limit (max 100) over 4-6 weeks.
Buy multiple seats, at least one per geo. Depends more on your TAM.
Keep all registrations from each webinar engaged through nurturing drips. Very important to grow month on month
The key also is cracking what topics and what speakers will click with your TG
Experiment with your messaging, and have multiple followup drips
You donot want them to mark you as spam especially with the new policies, ask them to reply back with unsubscribe instead.
I’ll be honest, it’s at a small scale. I am talking about generating 10-15 live attendees per webinar through outreach campaigns.